.2, W“ l ll‘lllll llllllllllllllllll 3 1293 100647 l l This is to certify that the thesis entitled THE EFFECTS OF CHRONIC ONE KIDNEY PERINEPHRITIC HYPERTENSION AND INTRAVENOUS ANGIOTENSIN II INFUSION 0N REGIONAL SPLANCHNIC HEMODYNAMICS IN THE DOG presented by Michael Craig Maier has been accepted towards fulfillment of the requirements for M. S. degree in Physiology Major professor Lisa/um m/ Date 11/8/79 0-7 639 y‘kuc—V OVERDUE FINES ARE 25¢ PER DAY PER ITEM Return to book drop to remove this checkout from your record. THE EFFECTS OF CHRONIC ONE KIDNEY PERINEPHRITIC HYPERTENSION AND INTRAVENOUS ANGIOTENSIN II INFUSION ON REGIONAL SPLANCHNIC HEMODYNAMICS IN THE DOG BY Michael Craig Maier A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Physiology 1979 ABSTRACT THE EFFECTS OF CHRONIC ONE KIDNEY PERINEPHRITIC HYPERTENSION AND INTRAVENOUS ANGIOTENSIN II INFUSION ON REGIONAL SPLANCHNIC HEMODYNAMICS IN THE DOG By Michael Craig Maier Regional splanchnic blood flows were measured in dogs using 85Sr, 51Cr and 141Ce during chronic hyper- microspheres labeled with tension (Series I) and before and after infusion of low (0.05 ug/Kg/min) and high (l.0 ug/Kg/min) dosescrfangiotensin II (Series II). During chronic hypertension blood flow remained unchanged in the adrenal gland, spleen and liver but increased in the pancreas. Blood flow was unchanged in the mucosal layers but elevated in submucosal and muscularis layers of the stomach, duodenum, jejunum, ileum and colon. Both doses of angiotensin II descreased blood flow in the pancreas, adrenal gland and spleen but liver was unchanged. Angiotensin II de- creased blood flow in all mucosal and submucosal layers of all regions of the gastrointestinal tract and produced an increase in muscularis blood flow in the duodenum and jejunum, while flow remained unchanged in the muscularis of the ileum and colon, and blood flow decreased in the stomach muscularis. DEDICATION To my mother and father for their continued support and guidance ii ACKNOWLEDGEMENTS I would like to take this opportunity to thank my advisor, Dr. Thomas E. Emerson, Jr., for the guidance and assistance he has provided in the pursuit of this research. I would also like to thank Dr. Jerry B. Scott and Dr. Ching Chung Chou for their assistance in the preparation of this manuscript. Finally, I would like to express my thanks and appreciation to Ms. Bonnie Beck for her support and patience. TABLE OF CONTENTS Page LIST OF TABLES .................................................. vi LIST OF FIGURES ................................................. vii INTRODUCTION .................................................... l SURVEY OF THE LITERATURE 3 The Use of Radioactive Microspheres in Chronic Vascular Research ......................................... 3 Experimental Renovascular Hypertension ..................... 4 Cardiac Output ........................................... 4 Vascular Compliance ...................................... 7 Blood Volume ............................................. 8 Regional Hemodynamics in Renal Hypertension ............... lO Renal .................................................... l0 Coronary ................................................. l2 Limb ..................................................... l3 Cerebral ................................................. l4 Splanchnic ............................................... l5 Role of the Renin-Angiotensin System ....................... l8 Early Renovascular Hypertension .......................... l8 Chronic Renovascular Hypertension ........................ 19 The Effect of Angiotensin II on Regional Splanchnic Blood Flow ................................................ 20 Summary .................................................. 23 METHODS ......................................................... 25 Series 1. Chronic Renal Hypertension ...................... 25 Surgical Preparation for Injection of Microspheres into Normotensive Dogs ....................................... 25 Preparation and Description of Stock Solutions of Microspheres ............................................ 26 Injection of Control (Chronic) Microspheres into Normotensive Dogs ....................................... 27 Surgical Induction of Perinephritic Hypertension ......... 27 Injection of Microspheres During the Chronic Hypertensive State ...................................... 28 Tissue Collection and Measurement of Radioactivity ....... 30 Calculation of Results ................................... 31 iv Page Series II. The Effect of Angiotensin II on Regional Splanchnic Blood Flow ..................................... 33 Surgical Procedure ....................................... 33 Description and Preparation of Stock Microspheres ........ 34 Experimental Procedure ................................... 34 Calculations of Results .................................. 35 Comparisons Made and Statistical Analysis of the Results ................................................. 37 RESULTS ......................................................... 39 Series I. Chronic Perinephritic Hypertension .............. 39 Chronic Control Values (Series I) gs, Chronic Hypertension Values (Series I ) ......................... 39 Acute Control Values (Series II) gs, Chronic Control Values (Series I) ....................................... 40 Acute Control Values (Series II) 3;. Chronic Hypertensive Values (Series I) ........................................ 41 Total Hall Blood Flow and Vascular Resistance Chronic Hypertension ............................................ 41 Regional Splanchnic Blood Flow and Vascular Resistance During Chronic Hypertension ............................. 43 Series II. Splanchnic Vascular Response to Intravenous Infusion to Angiotensin II ................................ 43 Total Hall Blood Flow and Vascular Resistance During Angiotensin II Infusion ................................. 43 Regional Splanchnic Blood Flow and Vascular Resistance During Angiotensin II Infusion .......................... 43 DISCUSSION ...................................................... 76 Hypertension Data .......................................... 82 Angiotensin II ............................................. 88 SUMMARY AND CONCLUSIONS ......................................... 95 BIBLIOGRAPHY .................................................... 99 Table LIST OF TABLES Page Average values of regional splanchnic vascular resistance (mmHg/ml/min/lOO gm) of the acute control dogs (control) vs. the chronic control dogs (experimental). (Mean + S. E. M. ) ............................................. 5l Average values for blood flow (ml/min/lOO gm) of the various abdominal organs of the acute control dogs vs. the chronic hypertensive dogs. (Mean + S. E. M. ) .......................... 56 Average values for vascular resistance (mmHg/ml/min/lOO gm) of the various abdominal organs of the acute control dogs .vs, the chronic hypertensive dogs. (Mean :_S.E.M.) .......... 59 Average values for blood flow (ml/min/lOO gm) of the various abdominal organs before (control) and after the intravenous infusion of low (0. 05 ug/Kg/min) and high (1.0 ug/Kg/min) pharmacological doses of angiotensin II. (Mean + S. E. M. ). ... 66 Average values for vascular resistance (mmHg/ml/min/lOO gm) of the various abdominal organs before (control) and after the intravenous infusion of low (0. 05 ug/Kg/min) and high (l. 0 ug/Kg/min) pharmacological doses of angiotensin II. (Mean :_S.E.M.) ............................................. 69 vi Figure 1 2a 2b LIST OF FIGURES Page Changes in unanesthetized mean arterial blood pressure during six week development of chronic experimental perinephritic hypertension .................................. 49 Average values for total-wall blood flow and mean arterial blood pressure (Pa) of the acute control dogs (open bars) gs, the chronic perinephritic hypertensive dogs (cross- hatched bars) ............................................... 52 Average values for total-wall vascular resistance and mean arterial blood pressure (Pa) of the acute control dogs (open bars) gs, the chronic perinephritic hypertensive dogs (cross- hatched bars) ............................................... 54 Average values for regional blood flows within the 6.1. tract and mean arterial blood pressure (Pa) of the acute control dogs (open bars) vs. chronic perinephritic hyper- tension (cross-hatched ban) ................................ 57 Average values for regional vascular resistance within the 6.1. tract and mean arterial blood pressure (Pa) of the acute control dogs (open bars) vs. chronic perinephritic hypertension (cross-hatched bar§T ........................... 60 Average values for total-wall blood flow and mean arterial blood pressures (Pa) during control (open bars), during intravenous infusion of a low dose of angiotensin II (cross- hatched bars) and during infusion of a high dose of angioten- sin II (dotted bars) ........................................ 62 Average values for total-wall vascular resistance and mean arterial blood pressures (Pa) during control (open bars), during intravenous infusion of a low dose (0.05 ug/Kg/min) of angiotensin II (cross-hatched bars) and during intravenous infusion of a high dose (1.0 ug/Kg/min) of angiotensin II (dotted bars) ............................................... 64 Average vlues for regional blood flows within the 6.1. tract and mean arterial blood pressures (Pa) during control (open bars), during intravenous infusion of a low dose (0.05 ug/Kg/min) of angiotensin II (cross-hatched bars) and during intravenous infusion of a high dose of (1.0 ug/Kg/min) angiotensin II (dotted bars) ................................ 67 vii Figure Page 8a 8b 8c Average values for regional vascular resistance within the 6.1. tract and mean arterial blood pressure (Pa) during control (open bars), during intravenous infusion of a low dose (0.05 ug/Kg/min) of angiotensin II (cross-hatched bars) and during the intravenous infusion of a high dose (1.0 ug/Kg/min) of angiotensin II (dotted bars) ............. 70 Average values for regional vascular resistance within the 6.1. tract and mean arterial blood pressure (Pa) during control (open bars), during intravenous infusion of a low dose (0.05 ug/Kg/min) of angiotensin II (cross-hatched bars) and during the intravenous infusion of a high dose (1.0 ug/Kg/min) of angiotensin II (dotted bars) ............. 72 Average values for regional vascular resistance within the 6.1. tract and mean arterial blood pressure (Pa) during control (open bars), during intravenous infusion of a low dose (0.05 ug/Kg/min) of angiotensin II (cross-hatched bars) and during the intravenous infusion of a high dose (1.0 ug/Kg/min) of angiotensin II (dotted bars) ............. 74 viii INTRODUCTION The use of the radioactive microsphere dispersion technique in chronic vascular research would prove to be very valuable because it would allow the measurement of regional hemodynamic parameters which cannot be measured by other means. To date, concrete data assessing the stability of microspheres lodged within vascular beds for an extended period of time is sparse. The report of Hales (1974) suggests that microspheres are not displaced from their initial sites of lodging during en eight-week chronic observation period. However, since the microsphere represents a foreign particle within an experimental animal, their ability to remain stationary after lodging within a vascular bed must be questioned. One purpose of the present study is to determine the stability of radioactive microspheres lodged within regional vascular beds of the Splanchnic circulation during an eight-week chronic observation period. The effect of chronic renovascular hypertension on the splanchnic circulation has not been clearly established. To date, investigations concerned with the role of the splanchnic circulation during chronic renal hypertension has produced conflicting results and a compartmental hemodynamic analysis of the gastrointestinal tract during the chronic hypertensive state is lacking. A second purpose of the present study is to investigate possible regional splanchnic hemodynamic changes within the mucosal, submucosal and muscularis layers of the gastrointes- tinal tract. While the effect of angiotensin II on the splanchnic circulation has been investigated somewhat extensively, a compartmental hemodynamic 2 analysis of the response of the gastrointestinal tract to this vaso- constrictor is lacking. Since angiotensin II is elevated for a period following severe hemorrhage and during early renal hypertension, a regional hemodynamic analysis might prove to be valuable in assesssing the role of angiotensin II during these pathophysiological states. A third purpose of the present study is to determine the effect of low and high pharmacological doses of angiotensin II on the splanchnic circulation and to provide a hemodynamic analysis of the response of the mucosal, submucosal and muscularis layers of the gastrointestinal tract. SURVEY OF THE LITERATURE THE USE OF RADIOACTIVE MICROSPHERES IN CHRONIC VASCULAR RESEARCH The radioactive labeled microsphere dispersion technique is an accepted technique for acute determination of blood flow to discrete regions of the body provided prescribed procedural criteria are adhered to strictly and microspheres of appropriate size are used t al. 1969). To date, two studies exist which suggest that the (Wagner use of radioactive microspheres in chronic vascular research is feasible. Kaihara gt_s1, (1968) measured possible loss of 50 u radioactive microspheres in dogs for a period of two weeks. Using external detectors urine and fecal material were monitored for a period of five days and total body radioactivity was measured for a period of two weeks. No change in total body radioactivity was found and radioactivity in urine and feces was negligible. These findings were indirectly supported by Hales (1974) in a comprehensive study which monitored microspheres in microcirculation of the rabbit ear for an eight-week period. Using a microscope and the ear window technique, he found that during the eight- week chronic period the spheres were not phagocytized, dislodged or otherwise removed from the area studied. While the microcirculation of the rabbit ear is different from other regional vascular beds, this study suggests that the use of microspheres in chronic vascular research is a feasible and valuable approach because, it enables each animal to serve as its own control thus minimizing variance. EXPERIMENTAL RENOVASCULAR HYPERTENSION TWo models of hypertension can be produced using the classical methods of Goldblatt g3_ g1, (1943): 1) Two kidney Goldblatt hyper- tension is produced by constriction of only one renal artery which produces a renin-dependent, mild, transient evaluation in arterial blood pressure; 2) One-kidney Goldblatt hypertension is produced by either constricting both renal arteries or by constricting one renal artery and removing the contralateral kidney. A volume-dependent state of hypertension is produced which is much more severe than that produced by the two-kidney model. The original Goldblatt method was modified in 1939 by Page, who found that wrapping one kidney in silk or cellophane, with or without contralateral nephrectomy produces a one-kidney or two-kidney Goldblatt model of hypertension, respectively. This method is called perinephritic hypertension and is apparently caused by an inflammatory reaction around the kidney resulting in a fibrotic encapsulation. While the actual mechanism of hypertension is unknown, it has been demonstrated that perinephritic hypertension and the classical Goldblatt hypertension are similar in every aspect (Pickering, 1972). This technique is often preferable since it does not involve clamp adjustment to obtain proper constriction of the renal artery. CARDIAC OUTPUT Extensive studies in animal models of experimental renovascular hyper- tension have shown that cardiac output is elevated during the first fbur weeks of hypertension, and total peripheral resistance remains normal. Subsequently, cardiac output gradually returns to normal while total 4 5 peripheral resistance increases. Ledingham _£.él: (1964, 1967) used electomagnetic flowmeters placed around the arch of the aorta to monitor cardiac output in anesthetized rats, before and after clipping one renal artery with contralateral nephrectomy, (one-kidney Goldblatt model). Cardiac output fell below control values for a period of five days after clipping, then increased transiently to a level above control values for the 35 day observation period. Interestingly, total peripheral resistance and blood pressure rose within two hours following renal artery constriction and remained elevated for the duration of the ex- periment. Ferrario _t.sl, (1970) used an electromagnetic flowmeter implanted around the aortic arch to monitor cardiac output in unanesthetized dogs before and after the induction of perinephritic hypertension. They produced a two-kidney model of Goldblatt hypertension by wrapping one- kidney in cellophane and leaving the contralateral kidney untouched. After a period of two weeks they converted the two-kidney model into a one-kidney model by contralateral nephrectomy. Cardiac output was elevated and total peripheral vascular resistance slightly decreased during the two-week period when the two-kidney model was in effect. Following the conversion to a one-kidney model, cardiac output rose further until it reached a maximum of 18% greater than the control level two weeks after nephrectomy. During this period, arterial blood pressure and for the first time, total peripheral resistance began to rise. Cardiac output transiently returned to normal by the fourth to sixth week post-nephrectomy and total peripheral resistance maintained the hypertensive state. 6 Ferrario _t_§1, (1974) compared the one-kidney Goldblatt hyper— tension model, produced by renal artery constiction, to his earlier studies of the one-kidney Goldblatt perinephritic hypertension model in unanesthetized dogs. One renal artery was constricted by a chronically implanted, externally adjustable clamp and the contralateral kidney was removed. Cardiac output rose during the first two weeks and remained elevated for a period of four weeks. An increased heart rate and, to a lesser extent, an increased stroke volume was responsible for the elevated cardiac output. During the first two weeks total peripheral resistance remained normal and the elevated arterial blood pressure was maintained solely by an increased cardiac output. Total peripheral resistance began to rise during the third week following renal artery constriction while cardiac output began declining. By the fifth week, cardiac output had returned to normal and hypertension was maintained solely by an elevated total peripheral resistance. These studies of Ferrario demonstrate that hemodynamic changes which occur in the perinephritic one-kidney hypertensive model and the one—kidney Goldblatt model produced by renal artery constriction are similar. In contrast to the findings of Ferrario, Bianchi sg_sl, (1970, 1972) found that cardiac output of dogs with one-kidney and two-kidney models of Goldblatt hypertension measured by dye dilution, rose more transiently. In the one-kidney model cardiac output was significantly increased on the fourth and seventh day following renal artery constriction. Also, total peripheral resistance rose immediately after renal artery con- striction but returned to normal after 24 hours. In the two-kidney model of hypertension, cardiac output was elevated for only one day fbllowing renal artery constriction and returned to normal by the sixth 7 and seventh days. Total peripheral resistance rose immediately after renal artery constriction and remained elevated throughout the one-week duration of the study. Elevated cardiac output with normal total peripheral resistance in the early hypertensive stage, and normal cardiac output with an associated increased total peripheral resistance in the chronic hypertensive state led to the "autoregulation theory" as an explanation for the development of hypertension (Coleman and Guyton 1969; Coleman gg_gl, 1971). Accord- ingly, vascular resistance increases in some or all peripheral regional vascular beds in response to the increased blood flow, eventually, re- sulting in a chronically elevated total peripheral resistance. To date, the regional autoregulatory function of various vascular beds is based upon short term animal experiments. The renal vascular bed maintains a relatively constant level of blood flow in the arterial blood pressure range of 80-200 mmHg. In the splanchnic circulation, autoregulation is present in the spleen, intestine, and hepatic artery circulation of the liver. There is no apparent autoregulation in the stomach (Texter §t_sl, 1968). However, the regional autoregulation of various vascular beds which occurs in response to the elevated cardiac output and arterial blood pressure is presently undefined. Therefore, it is uncertain how short-term regional autoregulation relates to long-term body autoregulation that has been suggested to occur in the course of the development of hypertension. VASCULAR COMPLIANCE Medial hypertrophy of arterial and arteriolar walls, thickening of the elastic intima, and an associated reduction in arterial compliance 8 are well established features of chronic experimental renal hypertension (Goldblatt 1938, Feigl, SE. 31, 1963). Recently, investigators have looked into the venous side of the circulation since a decrease in venous compliance could increase venous return to the heart and contribute to the elevated cardiac output during early hypertension. Overbeck (1972) studied pressure-volume relationships in the isolated, temporarily occluded segment of the jugular and femoral vein in dogs during the early (less than four weeks) stage of perinephritic hyper- tension. The pressure-volume curve of the femoral vein was shifted to-. ward the pressure axis, suggesting a reduced compliance, while the pressure-volume curve of the jugular vein remained unchanged. These findings were supported by Simon gt_ g1, (1975), who studied pressure-volume curves of mesenteric veins in two different models of hypertensive dogs during the early hypertensive stage. The pressure volume curve of the four week, one-kidney model suggested a decreased venous compliance while the pressure volume curves of the eleven day, two-kidney model remained unchanged. BLOOD VOLUME Ledingham and Cohen (1964) measured plasma volume and extracellu- lar fluid volume in rats with one-kidney Goldblatt hypertensions using the Evans blue distribution and thiocyanate method, respectively. Plasma volume and extracellular fluid volume tended to increase in both the hypertensive and the sham-operated controls, although the increases were significantly greater in the hypertensive rats at days three and seven. Plasma volume and extracellular fluid returned to normal by the fifteenth day following surgical induction of hypertension. 9 These findings were supported by Bianchi (1970), using similar techniques in conscious, unilaterally nephrectomized rats following renal artery constriction. A significant increase in plasma volume and extracellular fluid volume was found on days 1, 3-4 and 6-7 of hypertension; Plasma volume and extracellular fluid volume returned to normal by the twelfth, to fourteenth day. Ferrario gt_g1, (1970) measured plasma volume and total blood volume in dogs with one—kidney perinephritic hypertension using the radioiodinated serum albumen method. No change was found at 15 days after wrapping one-kidney in cellophane (two-kidney model), 15 days after contralateral nephrectomy (30 days post-wrapping), or after 10- 17 months of chronic, one-kidney, perinephritic hypertension. In contrast, Ferrario (1974) measured plasma volume and total blood volumes in conscious dogs with one-kidney Goldblatt hypertension using the lO-minute Evans blue dye dilution technique. He found a small, transient rise in plasma volume and total blood volume, accompanied by a fall in hematocrit, during the first two weeks after renal artery constriction and contralateral nephrectomy. REGIONAL HEMODYNAMICS IN RENAL HYPERTENSION There is little data in the literature concerning regional hemodynamics in one-kidney or two-kidney Goldblatt models of renal hypertension. Some investigators believe that in the chronic hyper- tensive stage, total peripheral resistance is increased uniformly throughout the systemic vascular bed and hence regional blood flows remain unchanged (Overbeck s§_._l. 1971, 1972a; 1972b; Simon ££..El- 1975). Other investigators support the theory that blood flow is redistributed between vascular beds during Goldblatt hypertension (Bralet st .21- 1973; Flohr gs .21- 1976). The results of long-term, total body autoregulation during an extended period of elevated cardiac output (early stage of hypertension) is also rather poorly understood. A review of available data follows. .3gggg Bonnous £3. 31, (1962) studied renal hemodynamics in chronic, two- kidney Goldblatt hypertension in anesthetized dogs. Direct measurement suggests that blood flow per unit weight is normal in the non-stenotic kidney and normal or decreased in the stenotic kidney, depending on the post stenotic blood pressure. Vascular resistance was elevated in both the stenotic and non-stenotic kidney, however, the rise was greater in the stenotic kidney. Consequently the rise in perfusion pressure is proportional to the rise in resistance. Using chronically implanted flowmeters, Ferrario £3..El- (1973) studied renal blood flow in conscious dogs with one-kidney Goldblatt hypertension produced by varying degrees of renal artery stenosis. Following a mild stenosis (i.e. 20%) of the renal artery, mean renal blood flow decreased during days 1-8, and then returned to or exceeded 10 11 control values. Pressure in the renal artery distal to the stenosis was lower than systemic arterial pressure, but greater than control systemic arterial pressure. Therefore, renal vascular resistance was initially elevated, but tended to return to normal after the first week following stenosis. Severe renal artery stenosis (i.e. 45%) produced a sustained reduction in mean renal blood flow and a sustained increase in renal vascular resistance. Bralet £I.§l: (1973) measured to the fractional distribution of 86Rb in conscious rats that had one-kidney 86 cardiac output using Goldblatt hypertension. Fractional distribution of Rb to the kidney of hypertensive was not significantly different from controls at periods of five and ten weeks of hypertension. Renal resistance was not reported. In a recent study, Flohr gg_gl, (1976) measured the fractional distribution of cardiac output using the radioactive particle dispersion technique in rats that had one-kidney and two-kidney Goldblatt hyper- tension fbr a period of eight weeks. In the two-kidney model, the stenotic kidney decreased in weight and received a proportionate decrease in the fraction of cardiac output which was less than normotensive control values. The opposite, untouched kidney increased in weight, re- ceived a proportionate increase in the fraction of cardiac output, and exhibited a resistance equal to normotensive controls. However, the total renal fraction of cardiac output for both kidneys in this model was not significantly different from control values. In the one- kidney model there was a considerable hypertrophy of the remaining kidney. The fraction of cardiac output increased, but not to the same extent as did the weight. Therefore, total renal fraction of cardiac 12 output and flow per weight of renal tissue were decreased when com- pared to control values in one-kidney Goldblatt hypertension. CORONARY Increase in myocardial weight, primarily due to left venticular hypertrophy, and increase in total coronary vascular resistance is a common feature of renovascular hypertension (West £2.21: L959). Whether coronary blood flow per unit weight of myocardium is altered during hypertension is uncertain. Dahners gt El- (1972) found an increase in fractional distribution of cardiac output to the heart in anesthetized, one-kidney Goldblatt hypertensive rats using labeled macroaggregated albumen. These find- 86Rb to measure ings were supported by Bralet gt_§l, (1973) who used fractional distribution of cardiac output in conscious rats that had one-kidney Goldblatt hypertension. Furthermore, they felt that cardiac hypertrophy only partly accounted for the increase in myocardial flow fraction; the fraction of cardiac output delivered to 1 gm myocardium was significantly greater in hypertensive rats and was proportional to the severity of hypertension. They hypothesized that the increases in myocardial fraction of blood flow reflects both cardiac hypertrophy and an increased nutritional demand of the myocardium during hyper- tension. 1 Conversely, Flohr st 21, (1976) measured the fractional distribu- tion of cardiac output to the myocardium using the radioactive particle dispersion technique in rats that had one-kidney and two-kidney models) of Goldblatt hypertension. Compared to normotensive controls, the myocardial fraction of cardiac output increased proportionally to the 13 increase in myocardial weight in both models of hypertension. Hence, flow per gramtrfmyocardium remained in the normal range. The coronary vascular resistance increased proportionally to the total peripheral resistance. .LL__ Limb hemodynamics have been intensively investigated in the early (less than 4 weeks) and the chronic (more than 4 weeks) stage of perinephritic hypertension in dogs by Overbeck gs_gl, (1971, 1972). They reported that limb hemodynamics in the early stage of hypertension are apparently similar to those in the chronic stage, including normal blood flow and increased vascular resistance. Also, the increase in total limb resistance was equally distributed between the skin and skeletal muscle vascular beds. Skin and muscle venous resistances were normal in both early and chronic hypertension. On the other hand, 86Rb to show that fractional distribution Bralet g3 Q1, (1973) used of cardiac output is reduced to the skin vascular bed and increased to the femoral muscle vascular bed in the rat during chronic on- kidney Goldblatt hypertension. Flohr gg_sl, (1976) measured the fractional distribution of cardiac output to skin and skeletal muscle using the radioactive particle dispersion technique in rats that had one-kidney and two-kidney models of Goldblatt hypertension. They found that the fraction of cardiac output received by the skin was equal to normotensive controls in both models of hypertension, hence skin vascular resistance increased pro- portionate to the increase in total peripheral resistance. In skeletal muscle, they revealed differences in the fractional distribution of 14 cardiac output in the one-kidney Goldblatt model, which exhibited a significant reduction in blood flow with an associated elevation in vascular resistance which was proportionately greater than the total peripheral resistance. This suggests a redistribution of blood flow from the muscle vascular bed to other organs in one-kidney Goldblatt renal hypertension. 0n the other hand, the two-kidney model, they found no significant change in muscle blood flow as resistance increased uniformly with total peripheral resistance. CEREBRAL Flohr _t_s1, (1971) studied cerebral hemodynamics in rats with three different types of experimental renal hypertension: two-kidney Goldblatt, one-kidney Goldblatt, and deoxycorticosterone with sodium chloride loading. They used the radioactive microsphere dispersion technique and expressed their results in terms of fractional distribution of cardiac output. Fractional cardiac outputs to the brain in all three hypertensive models were not significantly different from the normotensive control group. In each experimental model cerebral vascular resistance was increased in exact proportion to the increased systolic blood pressure, suggesting that regional vascular resistance of the cerebral vascular bed rises uniformly with total peripheral resistance. Flohr _£ El, (1976) later repeated and confirmed these studies using the same blood flow determination techniques in rats with one- and two-kidney Goldblatt hypertension. These studies imply that the cerebral vascular bed exhibits good autoregulation of blood flow during chronic renal hypertension. Strandgaard 23.21: (1975) studied the ability of the cerebral vascular beds of normotensive and two-kidney Goldblatt hypertensive 15 baboons to autoregulate blood flow during acute elevations in blood pressure. Cerebral blood flow was measured using the intracorticord 133Xe clearance method. Mean arterial blood pressure (MABP) was raised in increments of 10-20 mmHg by intravenous infusion of angiotensin II amide. Cerebral blood flow remained constant in the normotensive and hypertensive groups until MABP reached a level of 140-154 mmHg and 155-169 mmHg, respectively. Further evaluation of MABP in either group was associated with a proportionate increase in cerebral blood flow. The study suggests that the upper limit of cerebral blood flow autoregulation is elevated during two-kidney Goldblatt hyper- tension. However, a recent study suggests that the upper limit of cerebral autoregulation may be exceeded in chronic one-kidney perinephritic hypertension in dogs (Ely gt s1. 1977). Regional cerebral blood flow were measured using the radioactive particle dispersion technique in the same dogs before 6-8 weeks after the development of hypertension. Blood flow was significantly increased and vascular resistance was actually decreased in the hypothalamus, thalamus, and cerebellum. SPLANCHNIC Simon _g_gl, (1975) studied ileal blood flow and ileal vascular resistance in dogs during the early stage of one-kidney and two-kidney perinephritic hypertension. The one-kidney hypertensive model was hypertensive for a period of four weeks while the two—kidney model was hypertensive for a period of eleven days. Hypertensive animals were compared to sham-wrapped normotensive control dogs. Measuring blood flow directly on a per weight basis, they found ileal blood flow to be elevated by 20% in the one-kidney model. The two-kidney model showed 16 no significant increase in ileal blood flow. Combined ileal blood flow data from both models of hypertensive dogs resulted in a statisti- cally significant 17% increase in blood flow in the early hypertensive stage. Calculated ileal vascular resistance of both hypertensive models was not significantly different from the normotensive control. This data suggests that a portion of the elevated cardiac output passes through the mesenteric vascular bed during the early stage of hypertené sion. Since ileal vascular resistance was normal, the authors suggested that passive vasodilation does not occur despite elevated intravascular distending pressures. This finding suggests decreased vascular dis- tensibility in the hypertensive dogs. To date, two studies assessing regional splanchnic hemodynamic changes during chronic renovascular hypertension are available. Bralet gs _a_l_. (1973) measured the fractional distribution of cardiac output (86Rb) in normotensive and chronic one-kidney Goldblatt hypertensive rats. Compared to normotensive control values, chronic hypertension was associated with a normal fraction of cardiac output received by the liver, spleen, stomach and small intestine while the colon received an increased fraction of cardiac output during hypertension. These findings were partially supported by Flohre_t_ gl. (1976) who measured the fractional distribution of cardiac output (radioactive particle dispersion technique) in chronic one-kidney and two-kidney Goldblatt hypertensive rats. Compared to normotensive control values, the one-kidney hypertensive model exhibited a normal fraction of cardiac output received by the spleen and an increased fraction of cardiac out- put received by the colon. These results support Bralet s;_ 31, (1973). In contrast, Flohr sg_ g1, (1976) reported that chronic one-kidney l7 Goldblatt hypertension is associated with increased fractions of cardiac output received by the liver, stomach and small intestine while the adrenal gland received a normal fraction of cardiac output. The results of this study also suggest that the pattern of redistribution of cardiac output may also be dependent upon the model of renal hypertension studied. Compared to normotensive values, both models of chronic renal hypertension received normal and increased fractions of cardiac output in the adrenal gland and colon respectively. In contrast to the one-kidney Goldblatt, compared to control values the two-kidney model exhibited decreased fractions of cardiac output by the liver, spleen and pancreas while the fraction of cardiac output to the stomach and small intestine remained unchanged. ROLE OF THE RENIN-ANGIOTENSIN SYSTEM EARLY RENOVASCULAR HYPERTENSION Bianchi et_ Q1, (1970) measured plasma renin leves in the conscious, unilaterally nephrectomized dog after renal artery constriction (one- kidney Goldblatt model). Plasma renin levels, systemic blood pressure and total peripheral resistance increased sharply during the first two hours post—constriction. Plasma renin levels gradually returned to normal during 1-14 days following renal artery constriction, total peripheral resistance declined but systemic arterial blood pressure re- mained elevated. The authors suggested that hypertension might be produced initially by increased plasma renin and hence angiotensin II levels. Additional strong evidence that angiotensin II is responsible for the initiation of renovascular hypertension was provided by Miller 2; 31, (1972). Injection of a nonapeptide inhibitor of converting enzyme into unilaterally nephrectomized conscious dogs prevented hypertension which usually occurs after renal constriction. Inhibiting the converting enzyme was effective for only four days following renal artery constriction. After this period treatment with converting enzyme inhibition did not prevent the development of chronic hypertension. Angiotensin II may also play a role in increasing cardiac ouput during the initial days following renal artery stenosis. Angiotensin II stimulates adolesterone production and hence increased intravascular fluid volume in the one-kidney Goldblatt model (Oparil g3_ 91, (1974). Angiotensin II also appears to act directly on the central nervous system. Injection of angiotensin II is pharmacologic concentrations into 18 19 the arterial supply to the cross-perfused head of anesthetized dogs causes tachycardia and blood pressure elevation (Bickerton EL. 91, 1961). Scroop et_ g1, (1971) suspected the central site of action of angiotensin II to be in the area postrema of the medulla since this region lacks a blood-brain barrior. Systemic arterial blood pressure was measured during intravenous injections of angiotensin II and norep- inephrine in anesthetized dogs. Ablation of the area postrema signif- icantly reduced systemic pressor responses to angiotensin II but not to norepinephrine. CHRONIC RENOVASCULAR HYPERTENSION The role of the renin-angiotensin system in the maintenance of chronic renovascular hypertension is not well established. Since angiotensin II inhibitors are effect only during the first four days following renal artery constriction, and renin is only elevated during the initial onset of the early stage of hypertension, the possible role of the renin-angiotensin system in maintenance of the chronic (more than six weeks) stage of renovascular hypertension remains unanswered. However possible increased vascular sensitivity to normal circulating levels of angiotensin 11 during the chronic stage has been suggested (Bianchi 2: Q1, 1970). THE EFFECT OF ANGIOTENSIN II 0N REGIONAL SPLANCHNIC BLOOD FLOW The very potent vasoconstrictor angiotensin II is elevated during the first week following renal artery constriction or kidney wrapping in one-kidney and two-kidney models of Goldblatt and perinephritic hypertension respectively. It is also elevated for a period following severe hemorrhage. While there have been many investigations of the effect of angiotensin II on abdominal organs, a compartmental regional blood flow study of the response of the gastrointestinal tract to intravenous infusion of angiotensin II does not exist. Abell and Page (1942) first described the selective arteriolar vasoconstriction produced by natural angiotensin II. They implanted transparent moat chambers to allow direct microscopic examination of vascular changes in the ears of unesthetized rabbits. They found that with moderate doses of angiotensin, only arterioles constricted while venules and capillaries were uneffected. Texter £3. £1, (1964) studied the direct effects of several vaso- active agents on the segmental resistance of the mesenteric and portal circulation in dogs. They injected angiotensin II, l-epinepherine, levartenol, vasopressin, acetylcholine, methacholine, histamine and seratonin into the perfused superior mesenteric artery. It was reported that the mesenteric vasculature was more sensitive to vaso- constrictor than to vasodilator substances. Angiotensin II and vasopressin were the most potent vasoconstrictors and caused an in- creased resistance which was localized to the small vessel segment. Using jg,giggg techniques, Bohr and Uchida (1967) demonstrated the response of canine mesenteric arterial vascular smooth muscle to 20 21 different doses of angiotensin II. Helical strips of vascular smooth muscle were mounted in a bath of physiological salt solution at 37°C. Vascular responses to angiotensin were measured using a Grass displace- ment transducer. They reported that the threshold concentration of angiotenin required for tension development was 1-3 ug/L while maximum response was obtained with a concentration of 100 ug/L. When mesenteric vascular smooth muscle was treated with a high concentration of angiotensin, the tension at first increased rapidly, and reached a maximum in one to two minutes. After that period the tissue pre- paration gradually relaxed and had negligible tension remaining at the end of five minutes. If angiotensin was rinsed from the bath and the tissue allowed to recover for a period of 20 minutes, reexposure of the tissue to the same concentration of angiotensin produced tension development which was only one-third that of the original response. The authors proposed that these results were due to tachyphylaxis. These findings were supported by Shehadeh gs_ s1, (1969) who studied the effects of low and high pharmacological doses of angiotensin II on intestinal blood flow and motility in the dog. Superior mesenteric artery blood flow and intraluminal jejunal pressure were measured using electromagnetic flow meters and fluid-filled baboons respectively. The low dose of angiotensin was infused into the superior mesenteric artery at a rate of 0.05 ug/Kg/min for a period of seven minutes. The infusion rate was then increased to 1.0 ug/Kg/min for a second seven minute period. Vasoconstriction of the mesenteric vascular bed and a decrease in superior mesenteric artery blood flow occurred in a monophasic response which was maximal during the first two minutes while the low dose was infused. During the minutes 2-7 blood flow 22 increased but remained lower than control values. When the dose of angiotensin was increased during the minutes 7-14, blood flow did not change. Angiotensin increased jejunal motility during the entire duration of the experiment. To date, mechanisms that explain the effect of angiotensin II on gastrointestinal motility in the canine are lacking. However Khairallah and Page (1961) described possible mechanisms for the contractile response to angiotensin in the isolated guinea pig ileum. Visceral smooth muscle contraction was monitored using a frontal writing lever having fourfold magnifications. Prior to treatment with angiotensin, the guinea pig ileum was exposed to atropine and morphine which are known inhibitors of acetylcholine release at postganglionic parasympathic nerve endings. They found that these drugs inhibited the response of visceral smooth muscle to angiotensin as ileal motility was decreased by about 60-70%. These results suggest that angiotensin II increases GI motility primarily through an indirect manner, by increasing acetylcholine release at postganglionic para- sympathetic nerve endings in the myenteric plexus of Auerbach and plexus of Meissner. SUMMARY Currently available evidence suggests that the use of the radio- active microsphere dispersion technique in chronic vascular research is a feasible and valuable method. The responses of regional vascular beds to an extended period of increased cardiac output during one-kidney and two-kidney Goldblatt hypertension are quite variable. Investigators tend to agree that vascular resistance in the kidney and cerebral vascular beds rises proportionately with the general rise in total peripheral resistance during the chronic hypertensive state. They also tend to agree that during chronic renal hypertension, the increase in vascular resistance in the heart and colon is proportionately less than the rise in total peripheral resistance (hence increased blood flow). Studies of hemodynamics in other vascular beds are conflicting. It may be that the model of Goldblatt hypertension (one-kidney or two-kidney) used may also effect the results. A first purpose of this study is to investigate the hemodynamics of the splanchnic circulation during chronic one-kdieny perinephritic hypertension and to assess possible hemodynamic changes within the mucosal, submucosal and muscularis (muscle + serosal) layers of the gastrointestinal tract. Generalized vasoconstriction with an associated decrease in superior mesenteric arterial blood flow following the administration of angioten- sin II is a consistant finding. In the canine and guinea pig angioten- sin causes contraction of visceral smooth muscle resulting in an increased gastrointestinal motility. To date, the hemodynamic effect of angiotensin 23 24 II on the three layers of the canine gastrointestinal tract is lacking. A second purpose of this study is to measure the hemodynamic response of various abdominal organs and the mucosal, submucosal and muscularis layers of the gastrointestinal tract to the intravenous infusion of low and high pharmacological doses of angiotensin II. METHODS SERIES I. CHRONIC RENAL HYPERTENSION Healthy, conditioned male mongrel dogs (n=7) weighing 24 :_1 Kg were trained to lie quietly during femoral artery punctures for blood pressure measurements, which were conducted once each week throughout the study. Animals exhibiting resting mean arterial blood pressures of less than 140 mmHg on two separate occasions were accepted for surgical induction of hypertension. These criteria were established by Overbeck (1971). Conditioning included vaccination against rabies, dis- temper, leptospirosis, hepatitis, and examination of the stool for para- sites. The dogs were maintained on a diet of standard dog chow (Wayne Dog Food., Allied Mills Inc., Chicago, IL) pre and post-operatively and water is libitum. SURGICAL PREPARATION FOR INJECTION OF MICROSPHERES INTO NORMOTENSIVE DOGS Regional splanchnic blood flows were calculated using the radioactive particle distribution technique (Wagner g3_ 21, (1969). Animals fasted for 24 hours were anesthetized with sodium pentobartibal, (25 mg/Kg IV) and a cuffed endotracheal tube was inserted. Supplemental doses of sodium pentobarbital (50-100 mg) were given later if necessary, but no measure- ments were made during the first 30 minutes following administration. Mechanical ventilation was maintained with a Harvard positive pressure respiration pump (Model No. 607 Dover, Mass.). Respiratory rate was held constant at ten per minute, and tidal volume adjusted according to body weight. Room temperature was maintained at 23°C throughout all experimental procedure. Anesthetized animals were placed in a right lateral recumbency and 25 26 held in position by towel clamps attached to the webbing of the respective limbs. Under sterile conditions, a polyethylene cannula (PE 240) filled with normal saline was inserted into the abdominal aorta via the right femoral artery. This cannula was used for monitor- ing mean systemic arterial pressure when connected to a Stratham pressure transducer (Model 23Gb), obtaining arterial blood samples for analysis, and for reference blood samples collection during micro- sphere injection. A similar cannula, connected to a second Stratham pressure transducer, (Model 23 Gb) was inserted into the left ventricle via the left common carotid artery for the documentation of intraventric- ular placement and injections of microspheres. Pressure recordings were made using a Sanborn direct writing recorder (Model No. 7700). PREPARATION AND DESCRIPTION OF STOCK SOLUTIONS OF MICROSPHERES Three stock solutions of microspheres 15 1_5 u in diameter (3M 85 Company, St. Paul, Minn.) were labeled with either Strontium, 5lChromium or141Cerium and suspended in a 10% dextran solution )1 millicurie/lO ml) which contained one drop of TWeen 8O polyethylene sorbitan mono-oleate) to prevent microsphere aggregation. The specific activities for these isotopes were 13.73 mCi/gm for 85Sr, 10.42 mCi/gm 51 141 for Cr, and 7.61 mCi/gm for Ce. One milligram of the microspheres contained approximately 440,000 microspheres. Each dog received one m1 of each type of microsphere which represented an injection of approximately 3.2 x 106 microspheres with the 855r label, 4.4 x 10 6 51 6 Cr label and 5.7 X 10 microspheres with the microspheres with the 141Ce label. 27 INJECTION OF CONTROL,(CHRONIC) MICROSPHERES INTO NORMOTENSIVE DOGS One ml of preagitated, carbonized microspheres labeled with 85$r (15 :_5 u; 3M Company, St. Paul, Minn.) was withdrawn from the stock solution using a 3 ml syringe. This suspension was placed into a glass tube which contained 2 ml of a 20% dextran solution and mixed thoroughly using an ultrasonic sonifier cell disruptor (Branson Instrument Co., Long Island, NY) to achieve uniform dispersion of the microspheres. The microsphere suspension was then drawn into a 3 ml syringe and connected to the left ventricular cannula. Immediately prior to injection, mean systemic arterial pressure was recorded and an arterial blood sample was taken for analysis and recording of p02, and pCO2 using a radiometer blood gas analyzer. Blood hematocrit was determined using a centrifuged heparinized capillary tube. The microspheres were then injected as a bolus into the left ventricle and flushed with 5-8 ml of saline. At the time of injections, a three minute reference blood sample was withdrawn from the abdominal aorta into a heparinized syringe with a Harvard withdrawal pump at a rate of 3.88 m1/min. The reference blood was then divided into 12 gamma counting tubes (5 m1 capacity) at l m1/tube. The blood was frozen for later counting. The cannulae were removed, and the arteries were repaired with 7-0 cardiovascular suture. The incisions were closed with silk and ventafil suture. SURGICAL INDUCTION OF PERINEPHRITIC HYPERTENSION Immediately following the microsphere injection, perinephritic hypertension (Page 1939) was produced surgically. A left flank incision was made and the left kidney was exposed using a retroperito- 28 neal approach. The kidney was dissected free from it's perirenal fascia and fat and wrapped in silk. The silk-wrapped kidney, in turn, was wrapped in Saran Wrap to minimize the amount of adhesion between the kidney and the surrounding tissues. It was then restored to it's normal anatomical position and the wound closed by suturing tissues by layer. Procanine penicillin (60,000 units) and steptomycin (0.5 g) were administered intramuscularly for 3 days postoperatively. One week following the first surgery, a contralateral nephrectomy was performed under sodium pentobarbital anesthesia (25 mg/Kg IV) and sterile conditions. Animals were again treated 3 days postoperatively with antibiotics as described above. Aniamls were then maintained for a period of six weeks following the first documentation of sustained arterial hypertension (> 140 mmHg mean arterial pressure) recorded via direct puncture of the femoral artery in the conscious dog. INJECTION OF MICROSPHERES DURING THE CHRONIC HYPERTENSIVE STATE following a six week period of documented hypertension the terminal study was performed. Animals fasted for 24 hours were anesthetized with sodium pentobarbital (25 mg/Kg IV) and a cuffed endotracheal tube was inserted. Similar supplemental doses were administered under the same restrictions as mentioned above. Room temperature was held constant at 23°C. Ventilation was maintained by a Harvard positive pressure respiration pump, at the same settings used during the initial (8SSr) microsphere injection. A polyethylene cannual (PE 240) containing normal saline was inserted into the abdominal aorta via the right femoral artery for measurement of mean systemic arterial pressure, arterial blood gas sampling, and for withdrawal of the 3 minute reference 29 blood sample. A different procedure was used to enter the left ventricle of the heart for the 2nd and 3rd microspheres injections, prior surgery resulted in occlusion of the left common carotid artery. Unsuccessful attempts at placing the cannula into the ventricle via the right common carotid and brachial arteries in an unrelated group of practice dogs necessitated opening the left side of the chest in the fourth intercostal space for direct left ventricular puncture. Ely (1977) showed that cerebral blood flow was not effected by opening the thoracic cavity. The left common carotid artery, which was almost always occluded, was re-isolated and clamped to insure that no blood was flowing in this artery (as was the case when the artery was cannu- lated during the initial injection). A polyethylene tube (PE 240), attached to a pressure transducer and equipped with a 3-way stopcock and 13 gauge needle, was preparted for left ventricular puncture, documentation of intraventricular position, and injection of the second microsphere respectively. After the dogs stabilized, arterial blood gases were measured using a radiometer. The respiratory rate was either increased or decreased until the arterial pCO2 was identical to the pCO2 recorded during the initial microspheres injection. When the initial pCO2 was reached, 141 “Cr (15 1 5 u; 3M Company) was pre- a suspension of either Ce or pared as before, the selection being random. The syringe containing the microsphere suspension was then inserted into the 3-way stopcock and left ventricular puncture was performed. When intraventricular position was documented and mean systemic pressure was recorded, the microsphere suspension was injected into the left ventricle and a 3 minute reference blood samples was withdrawn at a rate of 3.88 ml/min 30 using a Harvard withdrawal pump. The reference blood sample was placed into gamma counting tubes as before and frozen. The animals, which now contain both 85Sr microspheres to measure normotensive regional 14] 5‘Cr microspheres to measure hyper- blood flows and either Ce or tensive regional blood flows were sacrificed by sodium pentobarbital overdose. TISSUE COLLECTION AND MEASUREMENT OF RADIOACTIVITY The abdominal cavity was opened through a ventral midline incision and the internal organs were exposed. Duplicate tissue samples were taken from the adrenal gland, spleen, liver, head of the pancreas, tail of the pancreas, fundus of the stomach, duodenum at the level of the pancreatic duct, proximal jejunum, terminal ileum and descending colon.' The segments of the intestinal tract were cut longitudinally and the lumens were exposed. All samples were washed with cold running tap water. Any external fat, fascia or mesentery which remained on the tissues were trimmed off. Each sample from the intestinal tract was then separated into three portions, i.e., the mucosa, submucosa, and the muscle plus serosa (muscularis). This dissection was accomplished by scraping the mucosa and muscularis from the submucosa with a blunt instrument. Each tissue sample, in duplicate, was placed into a pre- weighted plastic counting tube. The actual weight of each tissue sample was calculated after reweighing the counting tube. The tubes containing reference blood and tissues samples were placed in a Searle (Model 1185) gamma counter, and counted at the following settings: 31 ISOTOPE §A§§. WINDOW ATTENUATION 3551- 454 100 8 141 Ce 380 400 2 51Cr preprogrammed setting by Searle Co. The raw counts obtained from the Searle gamma counter were entered into a Wang Model 700 preprogrammed computer which removed overlap of the energy peaks of the three different isotopes which occurred between counting channels. CALCULATION OF RESULTS Regional splanchnic blood flow (rSBF) was calculated by dividing counts per minute (cpm) per gram of tissue by counts per minute of the three minute reference blood sample, and multiplying by the reference blood sample withdrawal rate (RBWR = 3.88 ml/min). ml/min/gm rSBF = cpmlgm tissue X RBWR cpm reference blood Regional blood flows were calculated for each tissue sample in the normotensive and hypertensive state. The regional blood flows of duplicate tissue samples were then averaged into regional blood flows (ml/min/lOO gm). Regional splanchnic vascular resistance (rSVR) was calculated by dividing the mean systemic arterial pressure (Pa) at the time of microsphere injection by the average regional blood flow (rSBF), (rSVR = Pa/rSBF). An average blood flow was calculated for each portion of the wall and total wall blood flow was calculated as the weighted average of the three layers. The weight distribution of the three layers is taken from the work of Yu 92 11. (1975). Total wall vascular resistance was 32 calculated by dividing total wall blood flow by systemic arterial blood pressure. SERIES II. THE EFFECT OF ANGIOTENSIN II ON REGIONAL SPLANCHNIC BLOOD FLOW SURGICAL PROCEDURE Male mongrel dogs (n=8), weighing 22 :_2 Kg were fasted for 24 hours prior to the experiment. The animals were anesthetized with sodium pentobarbital (25 mg/Kg IV) and a cuffed endothachial tube was inserted. Artifical ventilation was maintained with a Harvard positive pressure respirator. Respiratory rate was set at 15 per minute and the tidal volume was adjusted according to body weight. The animals were positioned in a right lateral recumbency. A polyethylene cannula (PE 240) was inserted into the abdominal aorta via the right femoral artery for the withdrawal of reference blood samples (Harvard withdrawal pump, 3.88 m1/min) and to obtain arterial blood for analysis of p02. pCOZ, and pH (Radiometer blood gas analyzer). A similar cannula was inserted into the left common carotid artery for the measurement of mean arterial blood pressure. Pressures were measured with Stratham pressure transducers (Model 23 Gb) and a Sanborn direct writing recorder (Model 7700). A similar cannula connected to a Stratham pressure trans- ducer (Model 23 Gb) and equipped with a 3-way stopcock and a 13 gauge needle was prepared for the documentation of left ventricular placement via puncture would of thoracic wall and myocardium and for injection of microspheres. A fourth similar cannula was placed into the right femoral vein for drug infusions. The animals were allowed to stabilize, and arterial blood gases (p02, pCOz) and pH were measured and recorded. The pCO2 and room temperature were held constant throughout the experiment. 33 34 DESCRIPTION AND PREPARATION OF STOCK MICROSPHERES 85 The microspheres used in Series II were again labeled with Sr, 51 141 Cr and Ce and were suspended in a 10% soluation of dextran (3M Company, St. Paul, Minn.). The microspheres had diameters of 13.7 :_1.0, 13.6 :_O.7, 14.1 1 0.8 respectively and specific activities of 11.89 mCi/gm, 40.76 mCi/gm, and 8.57 mCi/gm respecitively. One drop of TWeen 80 was added to each stock solution to prevent aggregation. One milligram of each stock solution contained approximately 440,000 microspheres. Each animal received an injection of 0.9 m1 of each stock solution which represented 3.3 X 106 microspheres labeled with 855r, 9.9 x 105 microspheres labeled with 5‘ Cr label and 4.6 x 106 microspheres with the 141Ce label. EXPERIMENTAL PROCEDURE The experimental procedure for Series II consisted of three micro- sphere injections to measure regional splanchnic blood flow changes that resulted from the administration of angiotensin II amide (microsphere partical dispersion technique). The first micorsphere injection measured control regional splanchnic blood flow at normal (anesthetized) blood pressure (approximately 130 mmHg). The control microsphere injection 14lCe. The procedures used in Series was randomized between 85Sr and II for microsphere preparation, injection and reference blood sample withdrawal were identical to the procedures used in Series I. After the first microsphere injection was completed a low pharma- cological dose of angiotensin II amide (10 ug/ml) was infused into the femoral vein (Harvard infusion pump at a rate of 0.5 m1/min for approx- imately 5 minutes to achieve a mean systemic arterial pressure in the 35 approximate range of 170-180 mmHg. This low pharmacological dose of angiotensin II was approximately 0.05 ug/Kg/min. When this pressure (51 range was achieved, a second microsphere Cr) was inected and a reference blood sample was collected. The 51Cr labeled was used consistently as the second microsphere injection because this isotope had a specific activity which was much 85$r and 141 higher than the Ce isotopes. Therefore, each 0.9 m1 of stock microspheres contained a smaller number of microspheres (990,000). This reduced number of injected microspheres is a possible source of error in blood flow measurement, so this isotope was used to measure blood flow that was felt to be a lesser importance. Following the completion of the second microsphere injection, the infusion rate of angiotensin II amide was increased to 2.0 ml/min for approximately 5 minutes to obtain a mean systemic arterial pressure of 200 + mmHg. This high pharmacological dose of angiotensin was approx- imately 1.0 ug/Kg/min. When this pressure was reached, a third micro- sphere injection was made and a reference blood sample was collected. The animals were then sacrificed and duplicated tissue samples were taken from the adrenal gland, head of the pancreas, tail of the pancreas, fundus of the stomach, duodenum at the level of the pancreatic duct, proximal jejunum, terminal ileum and descending colon as before. The samples were prepared weighted and the radioactivity measured in the same manner as described in Series I. CALCULATION OF RESULTS Average regional splanchnic blood flow and regional vascular resistance was calculated in the same manner described in Series I and 36 in the fbllowing equations. rSBF = cpm/gm tissue cpm reference blood rSVR = Pa rCBF X RBWR 37 COMPARISONS MADE AND STATISTICAL ANALYSIS OF THE RESULTS The present study consists of Series I and Series II. Series I measured the effect of chronic perinephritic hypertension on regional splanchnic hemodynamics. Values obtained from the microsphere injection at time zero which measured normotensive control blood flow will be referred to as Chronic Control values since they remained within the animals for an eight-week period during the development of chronic hypertension. Values obtained from the microsphere injection after the eight-week period during the chronic hypertensive state will be referred to as Chronic Hypertension values. Series II of the present study measured the effect of low and high pharmacological doses of intravenously infused angiotensin II on regional splanchnic hemodynamics. Values obtained from the initial microsphere injection which measured control blood flow prior to the administration of angiotensin will be referred to as Acute Control values. The second and third micrOSphere injection measured regional splanchnic blood during low and high doses of angiotensin respectively. 1. Chronic Control values of Series I were compared to Chronic Hypertension values for Series I using a Student's t-test modified for paired replicates. A "p" value of less than 0.05 was considered significant. 2. Acute Control values of Series II were compared to Chronic Control values of Series I using a Student's t-test. A "p" value less than 0.05 was considered significant. 3. Acute Control values of Series II were compared to Chronic- Hypertension values of Series I using a Student's t-test. A "p" value less than 0.05 was considered significant. 38 4. Acute Control values of Series II were compared to values obtained during low and high doses of angiotensin in Series II using a Student's t-test modified for paired replicates. A "p" value of less than 0.05 was considered significant. RESULTS SERIES I. CHRONIC PERINEPHRITIC HYPERTENSION Average values for unanesthetized mean systemic arterial blood pressure in the normotensive control and at each week following surgical induction of hypertension are shown in Figure l. The average unanesthe- tized mean arterial blood pressures were significantly greater than control (192 :_4 mmHg), at 2 weeks (166 :_5 mmHg), 3 weeks (177 :_7 mmHg), 4 week (181 1,10 mmHg), 6 weeks (185 :_12 mmHg), and 8 weeks (176 :_9 mmHg), following induction of hypertension by 29%, 37%, 40%, 43% and 36%, re- spectively (p < 0.05). CHRONIC CONTROL VALUES (SERIES 1) VS. CHRONIC HYPERTENSION VALUES (SERIES I) Average values for regional splanchnic blood flow before and after the development of chronic perinephritic hypertension are shown in Table 1. During chronic hypertension blood flow was significantly increased (p < 0.05) in the duodenum mucosa by 970%, duodenum submucosa by 161%, jejunum mucosa by 1080%, jejunum submucosa by 96%, ileum mucosa by 154%, ileum muscularis by 234%, colon submucosa by 236% and colon muscularis by 204% and decreased significantly (p < 0.05) in the liver by 108%. Average values for regional splanchnic vascular resistance before and after the development of chronic perinephritic hypertension are shown in Table 2. During chronic hypertension resistance was signif- icantly decreased (p < 0.05) in the duodenum mucosa by 104 %, ileum mucosa by 156%, ileum submucosa by 141% and colon muscularis by 218% and significantly increased (p < 0.05) in the stomach submucosa by 264% and in the stomach muscularis by 218%. Abnormally low mucosal blood flows values (Table l) and abnormally 39 40 high mucosal vascular resistance values (Table 2) of the chronic control dogs suggested that the validity of these data must be questioned since the ability of microspheres to remain within the splanchnic circulation for an eight-week period has not been documented. This necessitated the comparison of acute control values (Series II) to the chronic control data of Series). ACUTE CONTROL VALUES (SERIES II) VS. CHRONIC CONTROL VALUES (SERIES_I) Average values for regional splanchnic blood flow of the acute control dogs and chronic control dogs were shown in Table 1. Average blood flow values of the chronic control dogs were significantly lower (p < 0.05) in the duodenum mucosa by 823%, jejunum mucosa by 1062% and ileum mucosa by 210% and significantly higher (p < 0.05) in the pancreas head by 66%, pancreas tail by 84%, liver by 70%, stomach muscularis by 1297% and duodenum muscularis by 137%. Average values of regional splanchnic vascular resistance of the acute control dogs and chronic control dogs are shown in Table 2. Average resistance values of the chronic control dogs were significantly higher (p < 0.05) in the duodenum mucosa by 1246%, jejunum mucosa by 6958% and ileum mucosa by 220% and significantly lower (p < 0.05) in the stomach submucosa by 1080%, stomach muscularis by 93%, and duodenum muscularis by 120%. Since possible technical error or unknown phenomena was thought to be present in blood flow and resistance values of the chronic control dogs, the decision was made to compare chronic hypertensive values to the seemingly more reliable acute control values. The values of the acute control dogs were in better agreement with values reported by Chou and Grassmick(l978). 41 ACUTE CONTROL VALUES (SERIES II) VS. CHRONIC HYPERTENSIVE VALUES (SERIES 1) Chronic hypertensive values were compared to data of the more reliable acute control dogs in all of the following comparisons concerned with regional splanchnic hemodynamic changes that occur during chronic one-kidney perinephritic hypertension. In Figures 2A, 28, 3 and 4, open bars denote values of the Acute Control dogs, the cross hatched bars denote values of the Chronic Hypertensive dogs. Average mean arterial blood pressure was significantly greater (p < 0.05) in the chronic hypertensive dogs (164 1.10 mmHg) than the acute control dogs (137 :_5 mmHg) by 20%. TOTAL WALL BLOOD FLOW AND TOTAL WALL VASCULAR RESISTANCE DURING CHRONIC HYPERTENSION Average values for total wall blood flow in the stomach, duodenum, jejunum, ileum and colon and total wall vascular resistance in the same regions are shown in Figures 2A, and 28 respectively. There was no significant difference in average total wall blood flow or vascular resistance between the values of the six week hypertensive group and the acute normotensive control group in any region (p < 0.05). REGIONAL SPLANCHNIC BLOOD FLOW AND VASCULAR RESISTANCE DURING CHRONIC HYPERTENSION Average values for the blood flow of various abdominal organs of the acute control dogs of Series II and the six week chronic hyperten- sive dogs are expressed in Table 2. Blood flows of the chronic hyperten- sive dogs (p < 0.05) in any region studied (adrenal gland, head of the pancreas, tail of the pancreas, spleen and liver). Average values for regional blood flows within the gastrointestinal 42 tract are shown in Figure 3. Average blood flows of the hypertensive dogs increased significantly (p < 0.05) in the stomach submucosa by 320%, duodenum submucosa by 309%, duodenum muscularis by 130%, jejunum submucosa by 184%, jejunum muscularis by 212%. Regional blood flows were not significantly different (p < 0.05) from control in the stomach mucosa, stomach muscularis, duodenum mucosa, jejunum mucosa, ileum mucosa, ileum muscularis, colon mucosa and colon submucosa. Average values for the resistance of various abdominal organs of the acute control dogs of Series II and the chronic hypertensive dogs are expressed in Table 3. Resistance values of the chronic hypertensive dogs were not significantly different from the acute control dogs (p < 0.05) in any region studied (adrenal gland, head of the pancreas, tail of the pancreas, spleen and liver). Average values for regional vascular resistance within the gastrointestinal tract are shown in Figure 4. Regional splanchnic vascular resistance values of the hypertensive dogs were significantly lower (p < 0.05) than the values of the acute control dogs in the duodenum muscularis, jejunum submucosa, jejunum muscularis and colon submucosa by 106%, 199%, 136%, and 177% respectively. Regional vascular resistance values of chronic hypertensive dogs were not significantly different (p < 0.05) from values of acute control dogs in the stomach mucosa, stomach submucosa, stomach muscularis, duodenum mucosa, duodenum submucosa, jejunum mucosa, ileum mucosa, ileum submucosa, ileum muscularis, colon mucosa, and colon muscularis. SERIES II: SPLANCHNIC VASCULAR RESPONSES TO ANGIOTENSIN II The intravenous infusion of angiotensin II caused mean aortic blood pressure to rise significantly (p < 0.05) from control 136 1.5 mmHg) during the infusion of a low pharmacological dose (1976 :_mmHg) and during the infusion of a high pharmacological dose (202 :_5 mmHg) by 29% and 49% respectively. In Figures 5, 6, 7, 8A, 88 and 8C open bars denote values of the acute control dogs before the infusion of angiotensin, cross hatched bars denote values during the infusion of a low dose of angiotensin and dotted bars denote values during the infusion of a high dose of angiotensin. TOTAL WALL BLOOD FLOW AND VASCULAR RESISTANCE DURING ANGIOTENSIN II INFUSION Average values for total wall blood flows of the stomach, duodenum, jejunum, ileum and colon are shown in Figure 5. When a low dose of angiotensin was infused total wall blood flows were decreased signif- icantly (p < 0.05) from control in the stomach by 406%, duodenum by 177%, jejunum by 153%, ileum by 135% and colon by 60%. When the infusion rate of angiotensin was increased such that a high pharmacological dose was administered, total wall blood flows were decreased significantly (p < 0.05) from control in the stomach by 534%, duodenum by 198%, jejunum by 170%, ileum by 134% and colon by 46%. Total wall blood flows during the infusion of a low dose of angiotensin were not significantly different (p < 0.05) from total wall blood flows during the infusion of a high dose of angiotensin in any region of the gastrointestinal tract. Average values for total wall vascular resistances of the stomach, 43 44 duodenum, jejunum, ileum and colon are shown in Figure 6. When a low dose of angiotensin was infused, total wall vascular resistances were increased significantly (p < 0.05) from control in the stomach by 338%, duodenum by 238%, jejunum by 273%, ileum by 237% and colon by 120%. When the infusion rate of angiotensin was increased such that a high pharmacological dose was administered, total wall vascular resistances were increased significantly (p < 0.05) from control in the stomach by 650%, duodenum by 360%, jejunum by 334%, ileum by 318% and colon by 170%. Total wall vascular resistances during the high dose of angioten- sin were not significantly different (p < 0.05) from total wall vascular resistances during the low lose of angiotensin in the duodenum, jejunum ileum, and colon. However in the stomach, total wall vascular resistance during the high dose was significantly greater (p < 0.05) than total wall vascular resistance during the low dose of 71%. REGIONAL SPLANCHNIC BLOOD FLOW AND VASCULAR RESISTANCE DURING ANGIOTENSIN II INFUSION Average values for the blood flow of various abdominal organs during control and during low and high pharmacological doses of angioten- sin II are shown in Table 4. Blood flow was decreased significantly (p < 0.05) from control during the intravenous infusion of a low dose of angiotensin in the adrenal gland by 86%, head of the pancreas by 157%, tail of the pancreas by 140%, and spleen by 75%. During the infusion of a low dose of angiotensin blood flow was not significantly different from control (p < 0.05) in the liver. When the infusion rate was increased such that a high pharmacological dose of angiotensin was administered, blood flow decreased significantly from control (p < 0.05) in the head of the pancreas by 416%, and tail of the pancreas by 318%. 45 During the infusion of a high dose of angiotensin blood flow was not significantly different from control (p < 0.05) in the adrenal gland, spleen and liver. Blood flow measured during the infusion of a high dose of angiotensin decreased significantly (p < 0.05) from blood flow measured during the infusion of a low dose of angiotensin in the head of the pancreas and tail of the pancreas by 101% and 74% respectively, while in the adrenal gland, spleen and liver blood flow remained unchanged (p < 0.05). Average values for regional splanchnic blood flow during control and during infusions of low and high pharmacological doses of angiotensin II are shown in Figure 7. During the infusion of a low dose of angiotensin blood flow decreased significantly from control (p < 0.05) in the stomach mucosa by 473%, stomach submucosa by 146%, duodenum mucosa by 211%, duodenum submucosa by 44%, jejunum mucosa by 172%, jejunum submucosa by 143%, ileum mucosa by 130%, ileum submucosa by 148%, colon mucosa by 85%, and colon submucosa by 41%. During the low dose of angiotensin regional blood flow did not change significantly (p < 0.05) from control in the stomach muscularis, jejunum muscularis, ileum muscularis and colon muscularis. Regional splanchnic blood flow in- creased significantly (p < 0.05) from control during the infusion of a low dose of angiotensin in the duodenum muscularis by 122%. During the infusion of a high pharmacological dose of angiotensin blood flow was decreased significantly (p < 0.05) from control in the stomach mucosa by 625%, stomach submucosa by 89%, stomach muscularis by 107%, duodenum mucosa 250%, duodenum submucosa by 56%, jejunum mucosa by 199%, jejunum submucosa by 110%, ileum mucosa by 147% and ileum submucosa by 87%. Regional blood flows were not significantly different (p < 0.05) from 46 control during the infusion of a high dose of angiotensin in the ileum muscularis, colon mucosa, colon submucosa and colon muscularis. Regional splanchnic blood flow was increased significantly (p < 0.05) from control during the infusion of a high dose of angiotensin in the duodenum muscularis by 177% and jejunum muscularis by 68%. Regional blood flow during the infusion of a high dose of angiotensin decreased significantly (p < 0.05) from regional blood flow measured during the infusion of a low dose of angiotensin in the stomach submucosa by 44%. Regional splanchnic blood flows measured during the infusion of a high dose of angiotensin were not significantly different (p < 0.05) from regional blood flows measured during the infusion of a low dose of angiotensin in any of the other regions studied. Average values for the vascular resistance of various abdominal organs during control and during the infusion of low and high pharma- cological doses of angiotenin II are shown in Table 5. Vascular resistance was increased significantly (p < 0.05) from control during the intra- venous infusion of a low dose of angiotensin in the adrenal gland by 167%, head of the pancreas by 269%, tail of the pancreas by 207%, and spleen by 105%. During the infusion of a low dose of angiotensin vascular resistance was not significantly different from control (p < 0.05) in the liver. When the infusion rate was increased such that a high pharmacological dose of angiotensin was administered, vascular resistance increased significantly from control (p < 0.05) in the adrenal gland by 198%, head of the pancreas by 734%, tail of the pancreas by 550%, spleen by 151% and liver by 146%. Vascular resistance measured during the infusion of a high dose of angiotensin increased significantly (p < 0.05) from vascular resistance measured 47 during the infusion of a low dose of angiotensin in the head of the pancreas and tail of the pancreas by 126% and 112% respectively. There were no significant differences (p < 0.05) between vascular resistances during the infusion of a high dose of angiotensin and during the infusion of a low dose of angiotensin in any of the other regions studied. Average values for regional splanchnic vascular resistance during control and during infusions of low and high doses of angiotensin II are shown in Figure 8A, 88 and 8C. Regional vascular resistance was increased significantly (p < 0.05) from control during the infusion of a low dose of angiotensin in the stomach mucosa by 401%, stomach sbumucosa by 328%, stomach muscularis by 88%, duodenum mucosa by 339%, duodenum submucosa by 64%, jejunum mucosa by 370%, jejunum submucosa by 166%, ileum mucosa by 278%, ileum submucosa by 416%, colon mucosa by 140%, and colon submucosa by 88%. Regional splanchnic vascular resistance during the infusion of a low dose of angiotensin was significantly less than control (p < 0.05) in the duodenum muscularis by 31%. Regional vascular resistance was not significantly different from control (p < 0.05) in the jejunum muscularis, ileum muscularis, and colon muscularis during the infusion of a low dose of angiotensin. Regional vascular resistance was increased significantly (p < 0.05) from control during the infusion of a high pharmacological dose of angiotensin in the stomach mucosa by 750%, stomach submucosa by 416%, stomach muscularis by 193%, duodenum mucosa by 434%, duodenum submucosa by 88%, jejunum mucosa by 382%, jejunum submucosa by 130%, ileum mucosa by 328%, ileum submucosa by 166%, ileum muscularis by 444%, colon mucosa by 100%, colon submucosa by 90%, and colon muscularis by 229%. Regional splanchnic vascular resistance during the infusion of a high dose of 48 angiotensin was not significantly different (p < 0.05) from control in the jejunum muscularis and decreased significantly (p < 0.05) from control in the duodenum muscularis by 58%. Regional vascular resistance during the infusion of a high dose of angiotensin was in- creased significantly (p < 0.05) from regional vascular resistance during the infusion of a low dose of angiotensin in the stomach muscularis by 56%. There were no significant differences (p < 0.05) between regional vascular resistances during the infusion of a high dose of angiotensin and during the infusion of a low dose of angioten- sin in any of the other regions studied. .meammmeg coopn pmwempem came monocwu am2 commcmucquc we cowuuzucw Fmowmezm mmuocmc r--> .Afiuzv mmpmowpqmg umewma toe uw_ewvos ammulu m.pcmvzum mcwm: Foeucou o» cocoaeoo cog: mo.o v at .cowmcmpemaxc ovawggamcwema Foucwewcmaxm uwcogco we acmEgon>mu gem: xwm mcwgau meammmeq voopn megmugm come umNPSmsummcmca cw mmmcwgu .— weaned 49 Table 1. Average values for regional splanchnic vascular resistance (mmHg/mllmin/lOO gm) of the acute control dogs (control) gs, the chronic control dogs (experimental). (Mean :_S.E.M.) (Mean':_S.E.M.) N=ll N=ll Tissue Acute Control Dogs Chronic Control Dogs Adrenal Gland 0.05 :_0.04 0.67 :_ 0.13 Pancreas Head 4.67 :_0.97 2.56 :_ 0.52 Pancreas Tail 5.84 i 1.03 3.37 :_ 0.74 Spleen 1.35 :_O.32 1.26 :_ 0.21 Liver 10.86 :_2.81 5.22 :_ 1.06 Stomach Mucosa 2.32 :_O.46 3.14 i 0.70 Stomach Submucosa 44.94 113.21 3.81 :_ 0.74* Stomach Muscularis 29.96 :_4.41 15.27 :_ 2.3l* Duodenum Mucosa 1.22 :_0.10 16.42 i, 3.65* Duodenum Submucosa 33.43 1 7.81 38.73 1. 15.43 Duodenum Muscularis 29.89 :_4.27 13.58 i_ 2.63* Jejunum Mucosa 1.44 :_0.04 101.63 i_ 74.86* Jejunum Submucosa 30.69 1 5.05 49.57 g. 22.13 Jejunum Muscularis 34.36 i 6.92 137.29 :_106.85 Ileum Mucosa 1.27 :_0.29 4.07 :_ 0.75* Ileum Submucosa 25.52 :_6.87 28.42 :_ 6.57 Ileum Muscularis 31.37 :_8.53 50.49 i. 15.90 Colon Mucosa 1.14 1 0.14 69.67 1. 68.03 Colon Submucosa 10.51 :_1.63 11.92 :_ 3.39 Colon Muscularis 11.28 :_3.82 10.47 :_ 2.74 :_= S.E.M. (Standard Error Mean) * values of the two groups are significantly different (p < 0.05). 51 .Aeuzv pmmp-p m.p=aezpm a mcwm: AF—nzv mmzpm> Foeucou mason we“ on cmgmasou cog: .Amemn cucupm51mmoeov mace m>PmcmuLmaxz owpwgcamcwema o_eoE;u on» .m».amemp cmaov mmou Fogpcou musom ms» mo Away mgzmmmea noo_a meemugm come one gape woopn ppmzupmpop Low mw=_m> mmmem>< mod v as .mm mezmwd 52 23.: 222.5%... 222808 122951 N \ \ J 0 ¢ \ \ \\ s\ s. \ t E T . 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ION. 316805 ¢w_ .1. on. m V 535:3»... g “Hon. azeeflefluoae .228 D o: umOOllull-ulllu MO'H 000-18 53 .Anuzv pmmpnu m.ucmn:pm m mcwma Appnzv mwapm> Foeucoo mason ecu op umgmaeoo cog: .Amgmn cmsopmnummoguv mmou w>vmcmuemaa; uwpwgcamcwgma upcogzu ecu mm» Amemn cmaov mmou Foepcou mpsum esp mo Ammv mgzmmmea voopn meewpem came one mocmumvmmg empaomm> ppmzupmuop to» mm=Fm> mmmem>< mod v me .am mesmee 54 20400 2220.5 \ modva * 31650.». tom. u on. m v 53523»... § Breanne». «85 .228 _U leL. o q q o '5 N ... O ‘t onssg; whom /u1u1/|m/6H1u1u BONVLSISBH HV'IOOSVA 0. to 55 Table 2. Average values for blood flow (ml/min/lOO gm)of the various abdominal organs of the acute control dogs gs. the chronic hypertensive dogs. (Mean :_S.E.M.) ( Mean :_S.E.M.) N=1l N=7 Organ Acute Control Dogs Chronic Hypertensive Dogs Adrenal Gland 282.87 :_14.19 295.23 :_44.06 Pancreas Head 41.75 :_ 6.80 61.26 :_ 6.47 Pancreas Tail 32.50 i. 5.69 46.33 :_ 7.39 Spleen 143.75 :_27.95 99.66 1 14.88 Liver 19.09 :_ 3.34 15.62 :_ 3.78 * denotes values which are significantly different (p < 0.05). 56 .Aauzv bmmu-u m.u=me=pm a mcwmz APFqu mmon Poewcoo mpsom on» op umemanu cog: .Amgma venoumzummogov mmou w>wmcmugmazg owcoecu am» Amcmn :maov mmoc Foeucou mason on» mo “may mgzmmmea uoopn meempgm came new aumea chwpmmucwoeummm mzu cwguwz mzope noopn chowmme Low mmzpm> mmmgm>< mo.o v as .m weaned 57 COWS COLON COLON IOOOSA 311N150“ N8 COM 4 j ILEW W rum WCOSA woos NONI.“ um 11' i - g E i E 3 E 9 *9 £44 53 * §.\\\\\\\\\\s§ 35377 D So. \gg ..1x 11" C g2 1.35 mg g Volt) 5 Tito. g :00 ~ any a o>~ g o: a. .. “$1”: F L a; I .__|__1___L_111111114fi,1g1111J ooooooooooooooooooo N-OQOFQO¢MN-OD¢NN— whom / mus/1w ”101300018 58 Table 3. Average values for vascular resistance (mmHg/ml/min/lOO gm) of the various abdominal organs of the acute control dogs gs, the chronic hypertensive dogs. (Mean :_S.E.M.) (Mean :_S.E.M.) N=ll N=7 Organ Acute Control Dogs Chronic Hypertensive Dogs Adrenal Gland 0.05 :_0.04 0.65 :_0.12 Pancreas Head 4.67 :_0.97 2.82 :_0.28 Pancreas Tail 5.84 :_1.03 4.11 :_0.36 Spleen 1.35 :_0.32 1.93 :_0.36 Liver 10.86 :_2.81 25.81 :14.73 * denotes values which are significantly different (p < 0.05). 59 .Aauzv pmmp-b m.b=meaam m mcwmz ap_uzv moon FOEpcoo mason mzp op nmequoo cmgz .Amcmn umguum51mmoeuv moot m>wmcmuemazc owcogno aw».AmLmn cmaov mmon poepeou muzum mg» to Andy mezmmmea woo—a Powemuem came tam pumeu chwummpcvoepmmm mcp cwguwz mocmumwmme empaomm> Pocommmg mom mm:_m> mmmgm>< mod v a... .e mezmwm 60 25.53:! 38:33 «moo; Sum—.3 58:83m 309:3 gang 108:!» 300:: £39.38 (moo; 300:! 5:02.! «80:88» 300:. 238 23:: :38 1:3. 3:3. 3:3. ...-8:93 8326.. 2:ng 330:: £268 £1826 3380.51 3382.: go; 1 _ [a s . . é“- \\.I. V ......U x x , xx . a... . .x. t. . .. .. a .. . s t g “ Q \\ m \ \\\\\\\\‘ N\ 2.. x 4 E .... ... L .. 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(i Pa= I76 3 lmmHg) UM 2 D «x- p <0.05 1' DH-DL< 0.05 m High Dose Aluipa = 202 35mmHg) JEJ H m lllJJllllllllllljj wtuoocoVrNooofl'Noomfl-No IOIOIOIONNNNN ----- anssu whool/ugwnw/buww BONVLSISBU 65 Table 4. Average values for blood flow (ml/min/lOO gm) of the various abdominal organs before (control) and after the intravenous infusion of low (0.05 ug/Kg/min) and high (1.0 ug/Kg/min) pharmacological doses of angiotensin 11. (Mean :_S.E.M.) (Meanfi:IS.E.M.) Organ Control Low Dose High Dose Adrenal Gland Pancreas Head Pancreas Tail Spleen Liver 292.24 : 16.38 34.34 : 7.02 27.27 165.61 16.93 5.86 34.67 3.60 157.27 :19.23* 13.34 : 2.52* 11.35: 2.21* 94.63 13.69 + + 20.72* 5.02 225.321:.53.96 6.65: 1.4m 6.53: 1.43*+ 94.63 : 24.03 13.30: 5.40 * denotes values which are significantly different from control (p < 0.05) N=8. + denotes values of high dose which are significantly different from low dose (p < 0.05) N=8. 66 .Awuzv mmumuwpumg vmgwmq Low covewnoe ummuuu m_p:mn:um m mcwm: mmou zop ow cwgmasoo ems: .Awuzv mmpmowpame umgmma Low cowemuos_ummu-u m.ucmu:um m mcwm: Pogpcoo op nmgmaeou can: .Amgmn vmupouv HH :wmcmuowmcw $0 Acws\m2\ma o.Fv omen saw; a mo cowmaecp mzocm>mgucw newest vcm Amgma umgopm; -mmoguv HH cwmcmpowmcm mo Acve\m¥\mn mo.ov mmou zoF a mo cowmsch mzocm>meucw unrest .Amgon :maov Pocgcoo mcwgan “may mmgsmmwga voan pmwgmugm cams vcm yucca —m:wpmmpcwogpmmm on» cwguwz mzopm noopn pmcowmmg Lee mmspm> mmmgm>< mod v Q+ mo.o v 9.. .n mczmwm 67 0.25:0»:2 (80:20:... 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