TH PST} (LZ LIBRARY Michigan State University i“ This is to certify that the thesis entitled THE ROLE OF H1 AND H2 HISTAMINE RECEPTORS IN THE PULMONARY MECHANICAL, GAS EXCHANGE AND CARDIOVASCULAR RESPONSES OF NEONATAL CALVES T0 INTRAVENOUS HISTAMINE. presented by Ronald Francis Slocombe has been accepted towards fulfillment of the requirements for Master ' 5498130 in Science Department of Large Animal Surgery and Me 'cine \( 7! < ,*I ~ QXSUCCLW - Major professor Date August 6. 1979 0-7639 MSU LIBRARIES m 5 RETURNING MATERIALS: Place in book drop to remove this checkout from your record. FINES will be charged if book is returned after the date stamped below. THE ROLE OF 81 AND H2 HISTAMINE RECEPTORS IN THE PULMONARY MECHANICAL, GAS EXCHANGE AND CARDIOVASCULAR RESPONSES OF NEONATAL CALVES TO INTRAVENOUS HISTAMINE. BY Ronald Francis Slocombe A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Large Animal Surgery and Medicine 1979 ABSTRACT THE ROLE OF H1 AND H2 HISTAMINE RECEPTORS IN THE PULMONARY MECHANICAL, GAS EXCHANGE AND CARDIOVASCULAR RESPONSES OF NEONATAL CALVES TO INTRAVENOUS HISTAMINE. BY Ronald Francis Slocombe Histamine was administered by continuous intravenous infusion to three groups of anesthetized ventilated calves. Group I received hista- mine alone, Group II was pretreated with H1 antagonist and Group III with H2 antagonist. Histamine caused a decrease in cardiac output, increased heart rate and systemic and pulmonary hypotension. H2 receptors mediated pulmonary and systemic vasodilation and caused tachycardia. H1 receptor stimula- tion resulted in pulmonary vasodilation and decreased cardiac output without affecting heart rate. No H1 mediated effect could be clearly demonstrated on the systemic vasculature. In the lungs, histamine decreased dynamic compliance, increased air- way resistance, increased lung pressure-volume hysteresis and increased alveolar-arterial oxygen differences. It was concluded that the adverse effect of histamine on pulmonary mechanics and gas exchange results from H1 mediated constriction of small and large airways. Weak H2 mediated peripheral airway dilation was also demonstrated. ACKNOWLEDGEMENTS Special thanks to Drs. Mather, Coy, Riley and the Food Animal Faculty for their encouragement and support to allow completion of this work. A friend as well as an exemplary advisor, Dr. Robinson provided inspiration, guidance and endurance to a fledgling graduate student. My deepest gratitude is extended to this special human being. My appreciation is also extended to Roberta Milar for her painstaking efforts to teach technical skills to a graduate student with apparently many thumbs. Lastly, to my wife, JUdy, who in no small measure contributed to the completion of this work with her patience and enthusiasm. ii TABLE OF CONTENTS ACKNOWLEDGEMENTSOOOOO00......OOOOOOOOOOOOOOOOOOOOOOO00.0.00... LIST OF TABI‘ESOOOO0.00.....0.00.0.00...OOOOOOOOOOOOOOOOOOOOOOO LIST OF FIGURESOOOOOO...0....00.0.00...OOOOOOOOOOOOOOOOOOOOOOO I. INTRODUCTION AND LITERATURE REVIEW0.0000000000000000000000 RiSk FaCtors for PUlmonary Disease in Cattle........... Possible Role of Mediators in Physiologic Pulmonary Responses.............................................. Pharmacology of Histamine.............................. Control of in gigg Histamine Release................... Biological Effects of Histamine - The Lung............. Biological Effects of Histamine - Cardiovascular System Immunological Consequences of Histamine Release........ Purposes Of The St“dYooocoocoococoa-coo00.000.00.000... II MATERIALS AND METHODS...................................... Surgical Preparation................................... Measurement of Pulmonary Mechanics..................... Measurement of Gas Exchange and Cardiovascular Function Experimental DeSignoooooooooooooooooooo0000000000000... iii Page 11 vi 19 21 23 23 26 31 35 III IV VI VII TABLE OF CONTENTS (Cont.) RESULTS.................................................. Group I calves......................................... Group II calves........................................ Group III calves....................................... DISCUSSION AND CONCLUSIONS............................... Pulmonary Mechanics.................................... Gas Exchange........................................... Cardiovascular System.................................. SUMMARY.................................................. LIST OF REFERENCES....................................... APPENDICESOOOOOOOOOOOOOOOOOO00....OOOOOOOOOOOOOOOOOOOO0.. A. Equations used in calculation of indices described under the section "Materials and Methods".......... B. Mean values for variableSOOOOOOOOOOOOOO00.0.0000... iv Page 38 38 65 79 100 100 105 110 118 119 140 140 144 TABLE 4. 6. 7. 8. 9. 10. ll. 12. 13. LIST OF TABLES Statistical comparison between means for Cdyn' Raw! and Ptp in Group I calveseoeeeeeeeeooo00.000000000000000oeeoeo Statistical comparison between means for P-V hysteresis and PVEX in Group I calves.....eeeoeoeeeeooe00000000000000 Statistical comparison between means for Pa02 and (A-a) 02 differences in Group I calves-coo0.0000000000000000...o Statistical comparison between means for cardiac output, pulmonary artery pressure and pulmonary vascular IGSiStQDCB in Group I calves-00000000000000000000000000000 Statistical comparison between means for systemic arterial pressure, heart rate and stroke volume in Group I calves.. Statistical comparison between means for P-V hysteresis, PAOZ and PaCOz, Group II calves..............o............ Statistical comparison between means for systemic vascular resistance and systemic pressure, Group II calves......... Statistical comparison between means for heart rate, pulmonary vascular resistance and pulmonary artery pressure, Group II calves-0.00.0000.00000000000000.0000... Statistical comparison between means for Cdyni Raw! Ptp and P-V hYSteresiS' Group III calves..-00000000000000. Statistical comparison between means for Paoz and (A-a) 02 differences, Group III calveseoeoeo00000000000000.0000. Statistical comparison between means for cardiac output and strOke VOlumep Group III calveSOOOOOOOOOOOOOOOOO000.00 Statistical comparison between means for systemic arterial pressure and pulmonary artery pressure, Group III calves.. Statistical comparison between means for PCV, Hgb and T030, Group III caIVCSOOOeeeeeeeeoeeeoeeeooeeeooeeooeeoeeo Page 39 51 52 56 63 71 72 75 82 89 92 95 99 LIST OF FIGURES Figures Page 1. 3. 4. 7. 8. 9. 10. 11. 12. 13. Method for calculation of dynamic compliance (Cdyn) and airway resistance (Raw) from recorded tracings......................... 28 Method used in the calculation of static compliance (Cstat) from reccrded Pressure-VOIUNe traCingsooeoecoo-0000000000000....031 Schematic diagram of calf instrumentation for measurement of pulmonary mechanical and gas exchange variables..................33 Effect of histamine and vital capacity maneuvers on dynamic compliance (Cdyn) in Group I calveSOOOOQOooeooeeeeeeeoeooeoeeeco 41 Effect of histamine infusion and vital capacity maneuvers on airway reSiStance (Raw) in Group I calves..ooeeeoeoeeeeeeoeeeooe 43 Effect of histamine infusion and vital capacity maneuvers on maximal transpulmonary pressure (Ptp) in Group I calves......... 45 Effect of histamine infusion and vital capacity maneuvers on Pressure-Volume hysteresis (P-V hysteresis) in Group I calves... 48 Effect of histamine infusion and vital capacity maneuvers on peak expiratory flow (PVEx) in Group I calves..eeeeeeeeeeeoeeoee 50 Effect of histamine infusion on gas exchange in Group I calves.. 54 Effect of histamine infusion on pulmonary vasculature in Group I calves. Cardiac output, pulmonary vascular resistance and PUlmonary artery pressure................................... 58 Effect of histamine infusion on systemic vasculature in Group I calves.....eeeeeeeoeeeeeeeeeeeeeeeeeeoeeeeeeeeeeeeeooeeo 60 Effect of histamine infusion on cardiac output, stroke volume and heart rate in Group I calves.....OOO0.0.00.0...OOOOOOOOOOOOO 62 Typical tracing from a calf given a rapid intravenous bolus of the H1 antagoniSt, triPEIBHDamineooeeooeeecoco...00000000000000e 67 vi LIST OF FIGURES (Cont.) Figure 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. Effect of H1 blockade (tripelennamine) and histamine following H1 antagonism on pressure-volume hysteresis (P-V hYStereSiS) in Group II calveSooooooo00.000000000000000 Effect of H1 blockade (tripelennamine) and histamine following H1 antagonism on systemic vasculature in Group II calves...o.oo.coocooooooooooo00.000000000000000ooo. Effect of H1 blockade (tripelennamine) and histamine following H1 antagonism on pulmonary vasculature in Group II calves..coo-00000000000000.0.0000000000000000000000 The effect of H2 blockade (metiamide) and histamine following Hz antagonism on dynamic compliance (Cdyn) in Group III calves............................................ The effect of Hz blockade (metiamide) and histamine following HZ antagonism on airway resistance (Raw) in Group III calves.....0..0.0.00000000000000000000000.00...... The effect of H2 blockade (metiamide) and histamine following “2 antagonism on transpulmonary pressure (Ptp) in Group III calves..00000000000000.0000...00000000000000... The effect of H2 blockade (metiamide) and histamine following H2 antagonism on pressure-volume hysteresis (P-V hYSterQSiB) in Group III calveSOOOOOOOOOOOOOOOOOO0000.. The effects of H2 blockade (metiamide) and histamine following Hz antagonism on gas exchange in Group III calves. The effects of Hz blockade (metiamide) and histamine following Hz antagonism on cardiac output and stroke volume in Group III Calves......................................... The effects of H2 blockade (metiamide) and histamine following Hz antagonism on packed cell volume (PCV) total solids and hemoglobin concentration in Group III calves..... vii Page 70 74 77 81 84 86 88 91 94 98 INTRODUCTION AND LITERATURE REVIEW Pulmonary disease in cattle results in sickness and mortality, probably only second in importance to enteric disease. The development of lung disease may be favored by the environmental conditions typically encountered in calf rearing, and during normal management of the adult herd. There are, however, anatomical and physiological differences uni- que to cattle, that may favour the development of clinical disease. Some of these aspects are discussed in detail below. 1. Cattle have higher basal respiratory rates and minute ventilation than other animals probably as a result of a relatively small gas exchange surface area in relation to basal oxygen consumption (Altman and Dittmer, 1971; veit and Farrel, 1978). Respiratory rates may be further accelerated in heat stressed cattle (Esmay 1969). The factors may not only facilitate exposure to environmental hazards but may jeopardize gas exchange in the face of relatively minor distrubances in lung function. 2. Bovine lung differs anatomically from many species in that lung parenchyma is divided into discrete lobules (McLaughlin st 21, 1961: Mariassy £5 31, 1975). Interconnections between alveolar membranes, known as Pores of Kohn are of very limited number in cattle lungs (Mariassy gt El! 1975). Interconnections between adjacent lobules, known as collateral pathways have been described in dogs, cat, man and horses (Robinson and Sorenson, 1978: Woolcock and Macklem, 1971) but are absent in cattle. 1 Collateral pathways may deliver air to lung segments subtended by obstructed airways and maintain gas exchange. In species such as cattle, airway obstruction may have profound and lasting effects on gas exchange because of ensuing atelectasis. 3. In species with unlobulated lungs, collapse of a lobule tends to be prevented as a result of interdependence (tethering) by the surrounding lung (Mead st 21, 1970). In calves with loose interlobular connective tissue, interdependence may not occur and atelectasis may develop more readily than in other species (Sylvester st 31, 1975). As shown for isolated dog lung, (Robinson, manuscript in preparation) inter- dependence is least effective in the ventral lung fields. 4. During breathing, energy is required to stretch the lung and generate air flow. Work of breathing may become increased in pulmonary disease (Gillespie £5 at, 1964, 1966) and a decrease in specific conductance of cattle exposed to viral infection have been demonstrated (Kiorpes and Bisgard, 1978). Although studies on the work of breathing have not been conducted in naturally occurring cases of bovine pulmonary disease, it is likely that work of breathing increases. Increased work of breathing may limit growth and performance, and may compromise blood oxygen availability in species with a normally low total alveolar surface/basal oxygen uptake ratio. In addition, increased work of breathing may lead to respiratory muscle fatigue and further compromise lung function (Pardy st 21, 1979). 5. The bovine lung has been shown to have relatively few alveolar macrophages (Mariassy 22.21! 1975: Rybicka 25.21! 1974). Alveolar macrOphages function rely chiefly on energy generated by oxidative phosphorylation, a process dependent on the availability of oxygen (Leak 35 El! 1964; Stossel, 1974). Thus, the bovine lung is likely to have a limited alveolar macrophage response due to the small numbers available and because hypoxia created by terminal bronchiolar obstruction may reduce phagocytic activity. In addition hypoxia may depress the activity of the mucociliary transport mechanism (Laurenzi and Yin, 1970). That these effects of hypoxia are important in calves is supported by the finding that reduced bacterial clearance rates closely correspond to decreased regional oxygen tensions within the lung (Veit gt El! 1978). 6. Lysozyme is important in body defense mechanisms, particularly against infection (Jolles 1975, Stossel 1974). Bovine granulocytes and ocular secretions do not contain lysozyme (Padgett and Hirsch, 1969) and its presence has yet to be demonstrated in bovine lung secretions (Veit and Farrel, 1978). 7. Bovine pulmonary vasculature shows marked reactivity upon exposure to hypoxia (Grover £5 31, 1963; Kuida 23.21! 1962: Jaenke and Alexander, 1973). This may be an adaptive measure for, if the bovine lung suffers from a propensity to develop atelectasis (for the reasons previously discussed), pulmonary blood flow should be shunted away from hypoxic lung tissue in order to maintain blood oxygenation, ie. to minimize mismatching of ventilation and perfusion (Grant st 31, 1976). This response is thought to be under local control (Grant 2; El, 1976; Fishman, 1976) and chemical mediators, particularly histamine, have been incriminated in the rabbit, rat (Kay and Grover, 1975; Range and Melmon, 1968: Shaw, 1971), cat (Shaw, 1971: Range, 1969), mouse, guinea pig and sheep (Woods gt El! 1976). The role of histamine in hypoxic pulmonary vasoconstriction of dogs (Tucker st 31 1976, 1977: Giordano 23 31, 1977; Glazier and Murray, 1971), cats (Hoffman 35 El; 1977) and calves (Silove and Simcha 1973; Kay and Grover 1975) is currently controversial. The pulmonary hypoxic pressor response of calves has been shown to be modified by environmental (Will 32 El! 1978) genetic (Will 22 31, 1975; Weir gt El! 1974) and pharmacological influences (Silove and Grover 1968: Silove and Simcha 1973, Reeves £3 21, 1972) and not to diminish with aging (Bisgard gt 2;, 1972). The large numbers of mast cells in the bovine lung (Mariassy £5 21' 1975), with their attendant supply of mediators, may be a necessary component of vasoregulation in the face of local hypoxic stimuli (Fishman, 1976). However, in cattle exposed to reduced atmospheric oxygen tensions (as in high altitude environments) these mechanisms lead to the inappropriate responses of pronounced pulmonary hypertension and right heart failure (Alexander and Jensen, 1963; Grover £5 21, 1963). It remains unknown whether pneumonia in cattle is complicated by mediators released in response to local hypoxia. Cattle are exquisitely sensitive to histamine (Desliens, 1958; Nilsson, 1963.) Release of histamine as well as other mediators has been suspected in diverse disease conditions in cattle, including ruminal acidosis (Nilsson 1963; Ohga and Taneike, 1978) metritis and mastitis (Nilsson 1963, Zarkower and Norcross l966) acute interstitial pneumonia (Wilkie 1976, 1977, 1978: Moulton 33 21, 1963), Brisket disease, passive cutaneous anaphylaxis (Wells and Eyre, 1972) and generalized anaphylaxis (Eyre st 31, 1973). Although antihistamines are commonly used in the treatment of hypo- magnesaemia, an important role for histamine in this condition has not been substantiated (Henry 35 21, 1977). NOt only is histamine one of the putative mediators of anaphylaxis in cattle, but the lung has been demonstrated as the principle target organ of bovine anaphylaxis (Wray and Thomlinson, 1974; Aitken and Sanford, 1972). The importance of histamine and other chemical mediators remains to be determined for infectious bovine pulmonary disease. Histamine depresses the pulmonary clearance of bacteria (Gilka st al, 1974a, 1974b). The effects of histamine on gas exchange and the mechanical properties of the lung have not been studied in calves. Although a large volume of literature exists regarding the physiopharmacology of histamine in man, dog and guinea pig, cross species comparisons are likely to be inaccurate since the bovine lung exhibits marked anatomical and physiological differences as previously described. Pharmacology of Histamine Histamine was first synthesized in 1907 (Windaus and Vogt, 1907). It is a diacidic amine of molecular weight 111, readily soluble in water and stable under acidic conditions (Roth and Tabachnick, 1971). The first description of the (ni========C.CH2.CH2.NH2 pharmacological activity NH N of histamine was made in \\\\CH//¢ 1910 (Dale and Laidlaw, 1910), Histamine M.W. 111. and since that time there have been a great many reports concerning the biological activity of histamine. Histamine is not uncommon in nature (Mettrick and Telford, 1963) and can be found in plants as well as most animal tissues (Aviado and Sadavongvivad, 1970; Brocklehurst 1960: Eliassen 1973). In mammals, it is chiefly synthesized by tissue mast cells and basophils, but can also be synthesized by other cells (Wicki and Schatzmann, 1977), particularly in the fetus (Green 1962: Harrison 35 31, 1974). The biological importance of histamine is not well understood. It has widespread effects in most intact mammalian tissues, affecting smooth muscle in the cardiovascular, pulmonary, urinary, gastrointestinal and genital systems (Rocha e Silva, l966) Histamine stimulates exocrine gland secretion and may cause release of catecholamines from the adrenal medulla (Ploy-Song-Sang st 21, 1978, Roth and Tabachnick, 1971). It may have a physiological role in reproductive function (Marcus £2 31, 1963; Lerner and Carminati, 1977) and has been documented to cause excitation in the central nervous system (Monnier £3 21, 1967: Schayer 1974: Rosenburg and Savarie, 1964) and peripheral nerves (Chiou 25 31, 1976; McGrath and Shepherd, 1978). In addition, it appears to be a growth pro- motent found in high concentration in fetal tissues (Harrison, Peat and Heese, 1974) and in recovering foci of inflammation (Boucek and Noble, 1973: Kahlson and Rosengren, 1968). It has been incriminated in fetal cardiovascular responses during parturition (Woods 333 31, 1976). However, histamine is most frequently incriminated as a mediator of allergic and anaphylactic disease in a wide variety of species (Austen and Orange, 1975; Piper, 1977; Brocklehurst, 1960; Collier and James, 1967). Histamine release from mast cells is readily achieved using appropriate antigenic stimulation. A wide variety of known allergens, including moulds (Eyre, 1972), pollens (Bryant and Burns, 1976), pollutants (Said, 1978) bacterial toxins (Brown, 1965), venoms (Fredholm and Haegermark, 1968) and serum proteins (Metzger £5 21, 1978), may elicit mast cell degranulation under natural conditions. Many chemicals including 48/80 (Colebatch st 21, 1966), dextrans (Vaage 33 31, 1978), radiographic contrast media (COgen £5 21, 1978, Ring 35 21, 1978), sur- factants, antibiotics (Raab, 1968) and calcium ionophor also trigger histamine release. In the intact animal, histamine release may be affected by a wide variety of entities, including immunoglobulins (Vijay and Perelmutter, 1977: Grant 35 21, 1972; Ishizaka EE,2$' 1978; Weyer 35 21, 1978), complement fragments (Grant st 31, 1977), enzymes such as tryp- sin and chymotrypsin (Tolos st 21, 1975: Uvnas, 1963), phospholipase A (Damerau £5 31, 1975) prostaglandins, prostacyclines and thromboxanes (Engineer 35 21' 1978; Ercan and 'r'uirker, 1972; Walker, 1972), catecholami- nes (Kaliner gt 31, 1972), kinins and serotonin (McGrath and Shepherd, 1978). Exposure to hypoxia may also affect histamine release (Fishman, 1976). Control of the reactivity of basophils has recently been described in a number of species (Austen 3; 21, 1976: Lichtenstein, 1976). The control mechanism is believed to operate by alteration of cyclic nucleotide levels (Ortez, 1976: Orange, 1976). Modulation of histamine release can occur through the action of other mediators such as prostaglandins (Orange, 1976) corticosteroids (Lee, 1977), catecholamines (Moore, 1977) and acetyl choline (Reed 33 21, 1978). Furthermore, a rela- tionship between pulmonary airway reactivity and cyclic nucleotide con- tent in the lung has been demonstrated in rabbits (Kaukel £5 31, 1978) but not clearly identified in dogs (Barnett st 21, 1978). There are at least two binding sites for histamine, termed H1 and H2 receptors, which are responsible for histamine's biological activity (Chand and Eyre, 1975). Early studies concerning the biological effects of histamine utilized the common antihistamines, such as mepyramine, to block the conventional H1 effect. In 1972, the H2 receptor was described and found antagonized by a new series of inhibitors typified by cimetidine, metiamide and burimamide (Black 35 21, 1972, 1973). Recently, histamine was shown to exert an effect, in the face of both H1 and H2 antagonists, upon isolated equine tracheal muscle preparations (Chand and Eyre, 1977), suggesting the presence of an H3 receptor. The responses elicited by H1 and H2 receptor stimulation have been exten- sively reviewed by Chand and Eyre (1975). Not only are these receptors found in varying numbers in different organs, but their selective acti- vation results in marked alteration of organ function. Histamine modulates cyclic nucleotide levels (Math; gt‘gl, 1974: Lichtenstein and Gillespie, 1975; Polson £3 31, 1974: Lichtenstein, 1976; Kaliner, 1977: Reed 32 21, 1978). H2 receptor stimulation in the guinea pig (Math; 25 31, 1974) and human lung (Kaliner and Platshon, 1978) increases pulmonary levels of 3'5' adenosine monophosphate (cAMP). H1 receptor stimulation decreases cAMP. However, in dogs, histamine causes a net increase in cAMP in the lung mediated via H1 receptors (Barnett £5 31, 1978). H1 receptor stimulation also causes increased 3'5' guanosine mon0phosphate (cGMP) in the lung (Barnett st 31, 1978; Math; 22 21, 1974: Xaliner and Platshon, 1978). Similar increases in cGMP are also produced upon cholinergic stimulation (Kaliner, 1977; Kaukel st 21, 1978). In general, H1 receptor stimulation causes increases in cGMP and 10 decreases in cAMP, and H2 receptor stimulation increases cAMP in most tissues of a number of domestic and laboratory animal species (Chand and Eyre, 1975: Platshon and Kaliner, 1978). The implications of selective control of cyclic nucleotide levels, both in the release of and control by histamine within the lung, are far- reaching. The degree to which histamine participates in the various clinical forms of pulmonary disease remains to be clarified, and perhaps more importantly, it remains to be determined when participation of histamine in the pulmonary disease leads to exacerbation or amelioration of the condition. Biologic effects of histamine 1. mines Anaphylaxis in the guinea pig produces intense bronchoconstriction and histamine is thought to mediate this response (Collier and James, 1967) primarily through H1 stimulation (Bernauer st 21, 1968). Histamine induces contraction of both large and small airways, resulting in increases in airway resistance and decreases in dynamic lung compliance (POpa st 21, 1973: Drazen and Austen, 1974, 1975: Douglas 23 ‘21, 1973). While the reversal of bronchospasm with anticholinergic drugs has been documented (Drazen and Austen, 1975; Douglas 25 51, 1973, 1976), histamine has been shown to produce a peripheral constrictive effect refractory to vagal blockade in the guinea pig (Drazen and Austen, 1975) and cat (Cblebatch and Engel, 1974). In a study involving 11 three calves, Aitken and Sanford (1972,) observed that the clinical signs and postmortem findings of histamine given at 0.03 mg/kg intrave- nously did not appear to be reduced in severity after vagotomy in anesthetized calves. Similar studies do not entirely support this view, as it has been reported that vagotomy does prevent the initial apnea which occurs after histamine injection (Eyre £3 21, 1973). Alteration of the airway responses to histamine by interaction with catecholamines has also been demonstrated (Drazen, 1978; Collier and James, 1967: Pope £5 21, 1973: Douglas £2 21, 1973). In horses, similar H1 effects were reported in 1947 (Obel and Schmiterlow, 1947) and modification of the response to histamine by vagal blockade or catecholamine administration was noted. An H2 receptor-mediated bronchodilation was later identified for the horse in an in 31259 study (Chand and Eyre, 1977). Studies on the intact and isolated dog lung also indicate that hista- mine H1 receptor stimulation leads to constriction of both large and small airways and that effects on airway resistance can be counteracted by vagal antagonism (Kira and Rodbard, 1971: Jackson 2E.Ell 1978: Wasserman, 1975; Nisam £2 51, 1978). variability in the tonic vagal activity influencing the airways at the time of histamine exposure may alter the airway response to histamine (Loring £5 21, 1977, 1978; Benson and Graf, 1977). Histamine directly stimulates dog (Bleecker gt‘gl, 1976; Dixon st 21, 1978; Vidruk st 21, 1977), cat and rabbit lung irri- tant receptors (Mills gt 31, 1969: Hiserocchi st 21, 1978: Karczewski 12 and Widdicombe, 1969; Kaukel £3 21, 1978) but stimulation of neural receptors indirectly is also likely via changes in the permeability of the respiratory epithelium and by alteration of the mechanical and gas exchange properties of the lung (Kaukel st 21, 1978; Coon £5 31, 1978). Cross-species variability in the pulmonary response to histamine is well known. The bronchoconstrictive effect of histamine aerosols, as well as its release upon antigenic exposure, is well documented for man, dogs and monkeys (Math; 22 21, 1973: Frey and Gold, 1978: Michoud £2 ‘21, 1979: Simon et 21, 1977). The bronchoconstriction elicited upon antigen or histamine exposure is thought the result of H1 receptor sti- mulation (Casterline and Evans, 1977). In contrast, evidence from iso- lated muscle strips indicates that, in sheep, histamine causes weak, central airway bronchoconstriction mediated by H1 receptors and pro- nounced peripheral airway dilation as a result of H2 receptor stimula- tion (Eyre, 1975). Rats appear relatively resistant to the broncho- constrictive effects of histamine (Church, 1975: Kaukel £3 21, 1978). In man, histamine-induced bronchoconstriction causes decreased maximal and partial forced expiratory flows, decreased specific airway conductance (Rosenthal st 21, 1978), decreased vital capacity and increased closing volume and total lung resistance (Newball and Kaiser, 13 1973: Mitchell and Bouhuys, 1976). Cats exposed to histamine develop decreased dynamic compliance and increased airway resistance (Cblebatch 33 31, l966a, l966b). These observations would support the contention that, for most species studied to date, histamine can compromise lung function. In addition, histamine may cause these abnormalities to arise in naturally occurring cases of asthmatic lung disease in man. Hewever, disagreement still exists for it has been reported that changes in lung function tests in asthmatics may reflect prechallenge abnormalities in lung function rather than alterations in histamine reactivity between control and asthmatic patients (Brown‘s; 21, 1977a, 1977b). Studies on the pulmonary effects of histamine in cattle have not been extensive. Histamine is liberated $2.!iEE2 from bovine lung undergoing anaphylaxis (Eyre, 1971) and the cardiovascular changes of intact cattle undergoing anaphylaxis have been extensively studied. These studies have not addressed changes in gas exchange or mechanical properties of the lung. Anaphylaxis results in dyspnea, coughing and hyperpnea frequently preceded by a period of apnea and cyanosis (Aitken and Sanford, 1968, 1969; Ladiges £3 21, 1974, Wells 35 21, 1973; Eyre 22 21, 1973). Typical pulmonary lesions are congestion, hemorrhage, edema and patchy atelectasis, with degeneration and desquamation of alveolar epithelial cells and lymphatic distension (Wells 25 21, 1973: Ladiges 14 it 21, 1974). Sludging of granulocytes in the pulmonary capillary beds is also apparent (Wells e_t 21, 1973). Similar clinical and pathological signs have been produced by intravenous injection of histamine (Wray and Thomlinson, 1974: Aitken and Sanford, 1972) and have been reported in isolated lung studies (Lewis and Eyre, 1972). After an initial period of apnea, both histamine injection and anaphylaxis increase minute ven- tilation, tidal volume and respiratory rate as measured by Wrights respirometer or volume transducer methods (Burka and Eyre, 1974; Aitken and Sandford, 1969, 1972; Lewis and Eyre, 1972; Eyre 35 31, 1973). Histamine has also been demonstrated as important in passive cutaneous anaphylaxis in the calf (Wells and Eyre, 1972). However, disagreement still exists as to whether histamine is primarily responsible for the pulmonary signs seen in cattle undergoing anaphylaxis. Plasma histamine levels were found to increase in cattle undergoing anaphylaxis (Eyre st ‘21, 1973). However, this could not be demonstrated for other studies in cattle (Aitken 1970; Wray and Thomlinson, 1974). Furthermore, a protec- tive role for the classic antihistamines was identified in two studies (Eyre & Wells, 1973; Eyre st 21, 1973) but could not be supported by the findings of others (Aitken and Sanford, 1969, 1972: Wray & Thomlinson, 1974: Wells 22 21, 1974). Differences in challenge and sensitization procedures are unlikely to account for the current disagreement (Aitken e_t a_1, 1975). 15 Iglyitgg studies indicate that the bovine trachea and bronchus contract when exposed to histamine (Eyre, 1975; Kirkpatrick st 21, 1975: Bullock and Kirkpatrick, 1976). The respiratory effects of histamine infusion have been described in several studies, but none have addressed the problems of gas exchange and mechanical properties of the lung. In addition, some of the inferences concerning the respiratory effects of histamine are questionable. From clinical observations and measurement of minute volumes using a wright respirometer, Aitken and Sanford (1972) concluded that H1 antagonists blocked the respiratory effects of hista- mine, and that vagal activity was unimportant in the respiratory response. However, the studies were performed on pentobarbitol anesthe- tized calves. Pentobarbitol is known to depress the autonomic nervous system and has been demonstrated to alter the effects of histamine given to guinea pigs (Mordelet-Dambrine £5 31, 1977). In addition, stu- dies measuring minute ventilation were performed on four calves, including one vagotomized calf, and one calf premedicated with mepyra- mine. These limited numbers were too mall to allow statistical com- parisons between treatment groups. This study also involved the admi- nistration of lethal doses of histamine (0.03 mg/kg) and may not reflect the response of the lung to a physiologically realistic exposure. In a more extensive study, again with pentobarbitol anesthetized 16 calves (Eyre st 218, 1973), similar conclusions regarding the effects of histamine on ventilation volume were made. HOwever, this study did find that vagotomy reduced the apneic response caused by histamine. The stu- dies by Wells, Eyre and Lumsden (1973) and Lewis and Eyre (1972) did not explore the mechanism whereby histamine induces the change in minute volume, or for the increased inspiratory resistance noted for one iso- lated calf lung (Eyre gt 31, 1973). Finally, it has yet to be clearly demonstrated that the antihistami- nes as employed by wray and Thomlinson (1974), Aitken and Sanford (1969, 1972), Wells, Eyre, and Lumsden (1973), Eyre, Iewis and Wells (1973) can adequately antagonize the high local concentrations of histamine that could conceivably be achieved in lung tissue during bovine anaphylaxis. The conclusion that histamine is unimportant in bovine anaphylaxis, based solely on the failure of H1 antagonism to be protective for cattle undergoing anaphylaxis may be in error. 11 Vascular effects of histamine In vitro studies indicate that both the bovine pulmonary artery and vein constrict upon histamine exposure (Eyre, 1971, 1975). In 2122 histamine causes a marked decrease in systemic arterial pressure and a rise in pulmonary artery pressure (Aitken and Sanford, 1972: Eyre 32 21, 1973; Eyre and Wells, 1975: Lewis and Eyre, 1972). Reduction in heart 17 rate was reported for one calf in a study by Aitken and Sanford (1972) and was accompanied by a reduction in cardiac output (reported for two calves). However, in gitgg experiments using isolated perfused calf lung (Silove and Simcha, 1973) describe histamine induced pulmonary vasodilation, contrary to the findings of the above in 3132 studies. The systemic vasodepressive action of histamine in calves is largely, but not completely prevented by H1 antagonists (Eyre & Wells, 1973; Aitken and Sanford, 1972) indicating that the principle systemic effects of histamine are via H1 receptors (Elmes and Eyre, 1977). From studies on calves undergoing anaphylaxis, it was concluded that H2 receptor blockade potentiated the systemic vasodepressor effects, suggesting a pressor response for systemic H2 receptors (Eyre and Wells, 1973). Furthermore, it was suggested that the depressive action of histamine in calves that was unable to be blocked by H1 antagonism is not due to H2 receptors, but rather due to incomplete H1 blockade. This view has yet to be substantiated. Eyre and Wells (1973), and Chand and Eyre (1975) indicate that, from preliminary data, bovine pulmonary vasculature has H1 and H2 receptors that function with effects Opposite to those found in the systemic vasculature. The only data published to substantiate this view appears to concern an ig_!itrg experiment where H1-mediated contraction of pulmonary vein strips has been demonstrated (Burka and Eyre, 1974). 18 Histamine given to intact calves has also been shown to produce pulmonary edema (Lewis and Eyre, 1972; Aitken and Sanford, 1972; Gilka gt .21, 1974; Ladiges st 21, 1974). Similar edemogenic properties of hista- mine have been reported in sheep (Brigham, 1975; Harris gt El, 1978) and in guinea pigs (Aarsen and Zeegers, 1972). In sheep, the ability of histamine to induce pulmonary edema was blocked by H1 receptor antagonism (Brigham, 1975). The role of H1 and H2 receptors in the pulmonary and systemic cir- culation of domestic animals has recently been reviewed (Chand & Eyre, 1975). Considerable Species difference in the distribution and response of receptor types is apparent. In addition, receptor response has been shown to vary with the state of smooth muscle tone (Barer EE.El' 1976), histamine dosage (Barer st 21, 1976), and the type of anesthetic agent employed (Woods 33 21, 1977). A systemic depressor response mediated via H1 receptors and a systemic pressor response mediated via H2 receptors suggested to exist for calves (Eyre and wells, 1973) has also been described in horses (Hanna and Eyre, 1978) and guinea Pigs (Okpako, 1972a, 1972b; THrker, 1973; Goadby and Phillips, 1973). A similar role for H1 and H2 receptor responses has been described for the pulmonary vasculature of cats (Barer st 21, 1976). Although histamine produces similar blood pressure changes in both dogs and calves (Borst st 21, 1957), the response to H1 and H2 receptor stimulation in the systemic 19 vasculature appears opposite for these two species (Tucker £2 21, 1975). Systemic HZ receptor responses also appear different from the calf, for the chicken (Chand and Eyre, 1975) and the cat (Flynn and Owen, 1974) where H2 receptor stimulation causes systemic vasodilation. III Cardiac effects of histamine Bradycardia often accompanies anaphylaxis in cattle (Aitken and Sanford, 1969). The cardiac responses to histamine have not been criti- cally evaluated in calves. Results quoted by Aitken and Sanford (1972), were limited to single measurements performed once on two calves. Results were not subjected to statistical analysis. In dogs, H2 receptors exert a positive ionotropic effect as well as produce tachycardia, while H1 receptors exert a mild negative ionotropic effect (Tucker e_t _a_l, 1975). These findings are similar to those found in guinea pigs (Zavecz and Levi, 1978), but disagree with the conclusions of WOods gt 21 (1977), based on studies in sheep. IV Immunological modulation by Histamine Histamine has been demonstrated to modulate the inflammatory reac- tion and development of an immune response (Chand and Eyre, 1975). Histamine alters the responsiveness of neutrophils (Busse and Sosseman, 1976), eosinophils (Clarke 35 21, 1977), lymphocytes (Verhagen 32 El! 1977; Fox 23 31, 1979; Rocklin and Greineder, 1978; Plaut and Herman, 1978) and platelets (Allen and Eakens, 1978). Viral infections have 20 also been demonstrated to directly affect inflammatory responses (Buss £5 31, 1978), but it is not known whether they do so via alteration of mediator receptor sensitivity. In cattle, histamine is released from antigen-exposed leukocytes and lung fragments (Holroyde and Eyre, 1975, 1976a, 1976b, 1977). The release of histamine in bovine lung and leukocyte preparations is enhanced by H2 receptor stimulation (Holroyde and Eyre, 1977), unlike in man (Lichtenstein and Gillespie, 1973). The bovine granulocyte is also notably different from other species in that fl-adrenergic stimulation enhances rather than inhibits granulocyte release of histamine. The bovine granulocyte is also different in that it is inhibited by “adre- nergic stimulation (Holroyde and Eyre, 1976). This is the reverse of the findings for catecholamine modulation of histamine release in human and guinea pig basophils (Melmon and Bourne, 1974; Bourne st 21, 1974). Because of the unique modulation found in bovine granulocytes, blood borne leukocytes may serve to intensify inflammatory responses via a positive histamine feedback mechanism, rather than to lessen it as suggested in other species (Chand and Eyre, 1975). The bovine lung may thus be exposed to histamine released under allergic or infectious inflammatory processes, and perhaps exacerbated by involvement of basophils. 21 Exposure to histamine may also be increased due to abnormal ruminal function (Wicki & Schatzmann, 1977), estrus (Crouch and Godke, 1978), parturition and mastitis (Zarkower and Norcross, 1966; Zarkower, 1967a, 1967b). As discussed, clinical respiratory disease is of major economic importance in cattle. Physiological and anatomical differences in cattle may make them comparatively susceptible to the development and extension of pneumonia. Participation of histamine and other mediators has been described for a wide variety of conditions in cattle, but the importance of these mediators in the development and extension of disease states in the lung remains to be determined. In addition, pulmonary mechanical and gas exchange properties of the neonatal calf lung have not been studied in detail. There is a need to develop non- invasive pulmonary function tests for clinical and research purposes. Many of the techniques currently employed in human medicine are unsuitable for cattle, as these tests require alteration of patient breathing patterns upon request. The purposes of this study were to a. determine the normal pulmonary mechanical, gas exchange and car- diovascular properties of anesthetized neonatal calves, b. describe changes in cardiovascular, gas exchange and pulmonary mechanical properties of calves exposed to intravenous histamine diphosphate. 22 c. determine the relative roles of H1 and H2 receptors in the bovine response to intravenously infused histamine. d. develop a suitable experimental system for further research regarding mediator effects on lung function, and for deve10pment of pulmonary function tests suitable for adaptation to clinical situations. Anesthetized, fixed-volume-ventilated calves were instrumented for the study of the cardiorespiratory effects of intravenously infused histamine (Group I), histamine infused after H1 blockade (Group II) or histamine infused after H2 blockade (Group III). MATERIALS AND METHODS Purebred Holstein bull calves less than two weeks of age and weighing less than 55 kg were purchased locally. The absence of respiratory disease was confirmed by clinical examination prior to anesthesia, measurement of arterial oxygen tension (Paoz) prior to experimental studies, and by postmortem examination immediately following completion of data collection. Animals were not fed for 12 hours prior to an experiment. Two hours before anesthesia was induced calves received 1.5 liters of an oral multi-electrolyte preparation.1 Animals were anesthetized by intravenous administration of chloralose (100 mg/kg) and urethane (500 mg/kg) via a short catheter2 placed percutaneously in the right jugular vein. Induction of anesthesia was quiet if urethane were administered prior to the chloralose. Additional anesthetic was not required during the course of the experiment. After anesthetic induction, animals were promptly intubated using a cuffed endotracheal tube, and ventilated with a fixed-volume ventilator.3 Tidal volume was approximately 15 ml/kg body weight and respiratory rate was adjusted to provide an end expiratory carbon dioxide concentration of 4% to 5% as measured by an infrared analyzer which continuously sampled gas from the endotracheal tube.4 Animals were 1Ion-aid, Diamond Laboratories 2Venocath, Abbott 3Harvard Ventilator, Harvard Appliance Cb., Dover, Mass. 4Beckman LB-2 C02 Analyzer, Fullerton, Calif. 23 24 placed in sternal recumbency and given intermittent deep breaths to prevent atelectasis. With the exception of these maneuvers and during measurement of static compliance, tidal volume and ventilatory frequency were constant throughout the experiment. The left jugular vein and the left carotid artery were surgically exposed. A polyethylene catheter5 was placed in the carotid artery and a number 4 French, four side hole, Teflon catheter6 placed in the left jugular vein. Catheters were connected to pressure transducers7 and pressures were displayed on a oscilloscope and continuously recorded8 after signal amplification.9 Transducers were calibrated prior to each experiment against a mercury manometer. The jugular vein catheter was advanced until the tip lay in the pulmonary artery as verified by characteristic pulmonary arterial pressure tracings displayed on the oscilloscope. In two cases where difficulty was encountered in catheter positioning, pla- cement was performed under fluoroscopic guidance. Catheters were periodically flushed with heparinized saline.10I11 Pressure tranducers were placed at the level of the heart base (between the central and lower thirds of the chest). Transpulmonary Pressure Measurement An esophageal balloon catheter was made by perforating the distal 10 cm of a 100 cm Teflon catheter12 and attaching a 10 mm diameter, 10 cm 5Intramedic PE 190, Clay-Adams, Parsippany, N.J. 6United States Catheter and Instrument Corp., No. 5441, Glen Falls, N.Y. 7Statham P23 Db, Statham, Hato Rey, Puerto Rico 8Soltec Multipen Recorder Model B-38 II, Soltec, Sun Valley, Calif. 9PDV-22 Amplifier, Electronics for Medicine VR 6 Recorder, White Plains, N.Y. 1oSodium heparin, Sigma Chemical Cb., St. Louis, Miss. 11Particle free saline, Fisher Scientific, Idvonia, Mich. 12Cordis No. 8 French femoral catheter, Cbrdis Corp., Miami, Florida 25 long, thin walled, latex balloon to the distal end. The proximal 90 cm of the catheter were encased in a polethylene sleeve13 to provide sufficient rigidity to pass the catheter via the external nares into the esophagus. The balloon catheter was connected to a differential pressure transducer14 which was calibrated prior to each experiment against a water manometer. In order to measure transpulmonary pressure the other transducer port was connected via a similar 100 cm catheter to the endotracheal tube at the level of the animal's muzzle. A small volume of air (0.5 ml) was injected into the esophageal balloon, and the balloon positioned at the point in the distal esophagus where excursions of transpulmonary pressure were greatest during tidal breathing. Balloon construction, placement and response times to an effective square wave of 0-30 cm H20 (100% in .030 seconds) were similar to that described by Mead and Whittenburger (1953) and Milic-Emili st 21 (1964). In addition, frequency response characteristics of the esophageal balloon were balanced with those of the pneumotachograph, to minimize errors in dynamic compliance measurements attributable to phase lag between flow and pressure (Macklem, 1974) Transpulmonary pressures, systemic arterial pressure and pulmonary arterial pressure were continuously recorded using a multichannel pen recorder.8 Measurement of Gas Flows and Tidal Volume Inspired and expired gas flows were measured using a pneumotachograph15 attached to the endotracheal tube and connected to a .___..- 13Intramedic PE 320, Clay Adams, Parsippany, N.J. ”Statham PM 131, Statham, Hato Rey, Puerto Rico 8Soltec Multipen Recorder, Model B-38 II, Soltec, Sun Valley, Calif. 15Fleisch #1, Dynasciences, Bluebelle, Penn. 26 differential pressure transducer,16 amplifier and recorder.9 The pneumotachograph was calibrated at the termination of each experiment with a rotameter17 and blower. Tidal volume was measured by electronic integration of the flow signal. volume calibration was obtained by injecting known volumes of air through the pneumotachograph. Transpulmonary pressure, gas flow rates and tidal volume were recorded simultaneously on a light recorder for subsequent calculation of static compliance (Cstat.)' dynamic complicance (Cdyn)' airway resistance (Raw) and the difference between maximal and resting transpulmonary pressure (Ptp) . Mechanics of Ventilation 1. Cdyn and Raw were measured by the method described by Mead and Whittenberger, (1953). Briefly, dynamic compliance was calculated as the ratio of tidal volume and the change in transpulmonary pressure between points of zero air flow (figure 1a), at end inspiration and end expiration. Pulmonary resistance was calculated as the ratio of the change in transpulmonary pressures and change in flow rates between mid-inspiratory and mid-expiratory points of equal volume (figure 1b). 2. Static compliance. During recording of transpulmonary pressure, 200 ml. boluses of air, up to 1500 ml total, were injected18 then withdrawn from the lung. A pause of a least two seconds between each bolus allowed air flow to cease in the respiratory tract. The 16Statham PMS, Statham, Hato Rey, Puerto Rico 9PDV-22 Amplifier, Electronics for Medicine VR 6 Recorder, White Plains, N.Y. 17 1 Rotameter, Fischer and Porter 00., Warminster, Penn. Hamilton Syringe company, Whittier, Calif. 27 AV \mumAV.owusu on» was umusmsma mum mumnwvss >AVVca moocouwu .Bmm m>am on vocaauouwc ma . nuac .ossao> mesa Husvo mo mucwom Scum .3sm mcwumasoaso ca poms avenues we» mmumuuusaaa mp ousmam .cmvu 0>Hm on panamaoo son» as mAW>AV_mo Gauss we? .30Hm was Ohms no musaom kuowfloum Bouw pmusmmma was >V mesao> mesa can A>v .3Oamuau .Amumv moudmmoum xnmcosadmmcmuu mo mmcaomuu pmvuoomu aouw Azsmv museumfimou as3uflu was Achcov mossaamsoo owemshp mo scausasoamo you vogue: P MMDOHm lllrfllra .n.‘ .v .. .. I'M” 28 H mmonm m. .2..— 4.. '- ------------------ .2 IL 29 procedure was also repeated after three vital capacity maneuvers in which the lungs were inflated to a transpulmonary pressure of 30 cm H20 (Fig. 2a). From the transpulmonary pressure data and lung volume, a lung pressure volume curve was plotted. Static compliance was calculated from the slope of the expiratory limb between functional residual capacity (FRC) and FRC + 800 ml (Robinson 25 21, 1972). The area enclosed by the static pressure-volume plot was measured by planimetry19 (Fig. 2b). Pulmonary Gas Exchange and Cardiac Output Alveolar oxygen tension (PAoz), dead space/tidal volume ratio (Vd/Vt), alveolar-arterial oxygen difference (A-a D02) and cardiac output were calculated using blood gas tensions, blood oxygen content, and mixed expired gas composition. 1. Expired Gas Composition. Exhaled gases were collected in a Krogh Spirometer.20 The spirometer was flushed by twice collecting exhaled gas, before a third collection was taken for measurement of the mixed expired oxygen fraction21 (FEoz) and mixed expired carbon dioxide fraction4 (FEcoz) (see Fig. 3). Oxygen and carbon dioxide analyzers were calibrated prior to each experiment using standard gases of known composition. 19K & E Compensating Polar Planimeter, Keuffel and Esser Cb., Detroit, Mich. 20Warren-Collins Co., Braintree, Mass. 21Beckman OM-14 Oxygen Analyzer, Fullerton, Calif. 4Beckman LB-2 C02 Analyzer, Fullerton, Calif. 30 .Amaxs Hmowuuo>v > uncamms vmuuoam was Amwxs amusosauonv mum ca wwmcmnu .mssa may no uow>sn0n mammuwum»n can so mum>bmcma mufiosmmo Hmuw> mo Hummus ecu mmumuumdaaw use mooH oasHo> musmmmum owumum s Eouu umumo mo cofiumasoamo How venues onu mwnauomop mm enemas .A>V was «0 m0§5a0> szosx ands mead man no cofiumawmc usosvmmndm was coaumamsw mcausp A¢v scammed was Amumv unannoum auscosasmmcsuu cw mmmcmno mo msaosuu Hmoamwu m mmumuumsaaa «a madman .mmcwosuu wasao>lmusmmosm couscous Scum Aumumov oosnfiamabo owumum mo coausasoamo 0:9 ca cums vogue: N Hawah 31 N maze: not; \6 .Eu mmDmmwmn— 0” ON ON O- O- P b C ‘ «no D d d ‘ o o co 'BWH'IOA O O O 7w 000. DON. 00v. ; coo. .aeosaocoe 3.0:: .2.» 3:9! 6.2:...3... 3.9:: .2.» :32. 2. mm .3... 3 .3“. 32 .moanmwum> wasmnoxm mum use mocmfiamsoo caucus mo ucmfiuusmmms w>auommmmu mcaHdU Eoummm 0:» o» voxcwa 0Hw3 Hmuoaouamm was mmcflnhm 0:9 .coHHmn Hmmmmsmomw ha consumes .xmuonu 0:» ca was mausdfi on» as mmusmmmum sumsuwn wosmuwwuwv on» no someone“ was unammmum huMGOEHsmmcmuB .msfiao> aspen m>am Oman 0» vmumumousd ohms ammumonomuossmcm men mean: 3oaw mum mo mmsflouooms msoscwucoo .:Oaumuammmu amass: chHSU 30am Ham mucmmmummu suns pecans use .moanmwus> mmcmnoxm new use amoacmnowa humsoaasm mo ucmsuusmmwa sou cowusucwsnuumcw «H60 mo amummwv oeumfimsom m mmDUHh 33 m 5:5: _fl_m 34 2. Blood Gas Measurements. Blood samples were drawn anerobically into heparinized syringes from the pulmonary artery and carotid artery catheters during collection of the expired gas samples. Care was taken to draw large enough blood samples in order to minimize dilution effects of the anticoagulant (Sattler, 1969; Hansen and Simmons, 1977). Samples were immediately placed on ice and chilled until measurement of blood oxygen and carbon dioxide tensions,22 usually within twenty minutes. The blood gas analyzer was calibrated for each pair of samples (carotid and pulmonary arterial blood) using standard solutions and gases. Blood gas tensions were corrected to body temperature (Nomogram from Severinghaus, J.W.) as measured by rectal thermometer probe.23 Percent saturation of hemoglobin was measured with an oximeter24 calibrated against an opti- cal standard. At the time of blood withdrawal for blood gas analysis, blood samples were also placed in EDTA coated blood collection vials. These samples were later used to determine hemoglobin concentration.zsr26 Alveolar oxygen tensions were calculated using the alveolar gas equation. Cardiac output was calculated using the Pick principle, and from measurement of heart rate, systemic arterial and pulmonary arterial pressure at the time of blood sampling, stroke volume, systemic vascular resistance and pulmonary vascular resistance were calculated. 22Radiometer Copenhagen Blood Micro System BMS3 Mk 2, The London Cbmpany, cumum,mm 23YSI Telethermometer Model 41 TF, Yellow Springs Instrument company, Inc Yellow Springs, Ohio 24A.O Micro-Oximeter SM 2700, American Optical Co., Buffalo, N.Y. 25Internaltional Microcapillary Centrifuge Model MB., International Equipment Company, Inc., Boston, Mass. 26Fisher Haemophotometer, Fisher Scientific Co., Pittsburgh, Penn. 35 Alveolar-arterial oxygen differences and dead space/tidal volume ratios were also determined. (Equations used in all calculations are listed in Appendix 1). Experimental Design All animals were anesthetized and instrumented as described. All measurements described above were made repeatedly in the three groups of calves as outlined below. Statistical Analysis Data were analysed in a two way analysis of variance using each animal as its own control, in a completely randomized block experimental design. All calculations were based on the .01 significance level. Mean differences were statistically compared using Tukey's w procedure (Steel R.G.D and Torrie J.H. 1960). Group I After control measurements were taken, histamine diphosphate was continuously infused27 via the previously placed right jugular indwelling catheter using a constant rate infusion pump.28 Infusion rates were increased until at least a 50% increase in transpulmonary pressures was noted during tidal breathing. Once a steady state was reached, data were collected. Further measurements were taken 15, 30 and 60 minutes after cessation of histamine infusion. In four animals, blood was taken, 27Histamine diphosphate, Sigma Chemical Co., St. Louis, Miss. 28Infusion Pump Model 940, Harvard Apparatus Co., Millis, Mass. 36 immediately centrifuged29 and the plasma separated and frozen for subsequent histamine analysis. (Courtesy: Dr. Ken Mathews, Allergy Section, Medical School, university of Michigan, Ann Arbor, Mich.). In all group I calves, peak expiratory flows were determined by measurement of the maximal flows recorded during passive exhalation. Group 1; After control measurements were taken, calves were given a single intravenous bolus of the H1 antagonist, Tripelennamine, at a dosage of 5 mg/kg. Measurements were repeated 15 minutes after the bolus was injected. Adequacy of H1 antagonism was assumed when the rapid intravenous administration of the H1 agonist PEA31 at a dosage of 50 mcg/kg produced no observable change in either systemic or pulmonary arterial blood pressure, or transpulmonary pressure. Histamine was then infused at a dose similar to that used in the first group of calves. Once steady-state conditions were achieved, measurements were repeated. The infusion rate of histamine was doubled, and further measurements taken. Additonal measurements were made 15, 30 and 60 minutes after the infusion of histamine ceased. Group III Following control measurements, calves were given a single intravenous bolus of the H2 antagonist, Metiamide32 at a dosage of S 29International Clinical Centrifuge Model CL, International Equipment Co., Needham Heights, Mass. 3oTripelennamine, CIBA Chemical Cb. 31PEA, Courtesy: Smith Kline & French, Philadelphia, Penn. 32Metiamide, Courtesy: Smith, Kline and French Laboratories, Philadelphia, Pa. 37 mg/kg. Fifteen minutes after the injection, measurements were made. Adequacy of H2 antagonism was assumed when the rapid intravenous admi- nistration of the H2 agonist, Dimaprit33 (Schaff and Beaven, 1977) at a dosage of 50 mcg/kg produced no observable change in blood pressures or transpulmonary pressure. Histamine was infused as previously described, and the rate adjusted until at least a 50% increase in transpulmonary pressure occurred. Additional measurements were made at 15, 30 and 60 minutes after the infusion of histamine had ceased. Blood samples withdrawn for measurement of hemoglobin content, as previously described, were also used in the determination of haematocrit25 and total solids, as measured by refractometer.34 33Dimaprit, Courtesy: Smith, Kline and French Laboratories, Philadelphia Pa. 25International Microcapillary Centrifuge Model MB, International Equipment Cb., Boston, Mass. 34American Optical Co., Buffalo, N.Y. RESULTS A. Group I Histamine diphosphate was infused into five calves, at an average dose rate of 24.4 mcg/kg/min of histamine base (range 15.2 to 38.0 mcg/kg/min). Cardiovascular, gas exchange and pulmonary mechanics variables were measured during five periods, designated as follows: ”Control” - prior to histamine infusion. ”Histamine" - during histamine infusion, after steady state conditions had been reached. '15-PH”, ”30-PH' and '60-PH” - respectively 15, 30 and 60 minutes after the infusion of histamine had ceased. All comparisons between means were conducted at the .01 significance level. 1) Effect pp Pulmonary Mechanics Infusion of histamine failed to alter Cstat (for mean values of all measurements see Appendix B) but decreased Cdyn. to less than half its control value. After vital capacity maneuvers (v.c.) ”histamine” and control Cdyn. values did not differ (see Fig. 4, table 1a). Histamine caused a greater than two fold increase in Raw (Fig. 5) and Pt (Fig. 6). Vital capacity maneuvers did not alter the effects of P histamine on Raw (table 1b) and after vital capacity maneuvers, Ptp measurements were not significantly different from mean ”control” Ptp values. 38 39 Hm>0a Ho. on» us unmowmacmflw madmoaumwusuu no: mum mafia 08mm an concomuwvss acme: a v..o~ oe.o. o~.o. vo.m mm.m n~.m em.s me.s ea.» mw.o mafiamumnm mmnmp u> mcsanumnm manom Houucoo sauce o> maump o> Houucoo o> mmuom u> amuse a... 6... .mo. omo. mmo. .mo. ~so. moo. moo. mmo. assauumam op mcsauumsz o> maump o> zmuom manmp zmuom o> mauoo sauce o> Houucoo Houucoo 3 . apncns.muusaxo~m sue mm n m.m~. s.m~. m.m~. m.o.. _.mm o.mm o.~m ~.om m.os 6.5m D> mmlow U> mmlmp U> mmlom U > HOHHCDU HOHUCOU mmlom U>IOCHEdUmfim mmlom mmlm— ¢OCHEUumfim EN: .835 E6 u .. .mm>amo H mdoum :a mum use .3mm .chou Mow memes cumsumn condummEoo Hmoaumwumum w mamdfi ho .Ho>ma wosmoauwcmwm as. we» now umumasoamo mum mama House uumssmum .cmmsmo Us: coamsuca meassumwn nevus moussfia om n mmuom .ewmmmo on: coemsuas mcasuumsn noun. amuscss on u manom .ummmoo on: scamswcw unassuman nouns nuances ma u mmlma mumg3 mfixu asucouwuon man so Umuuon ohm muoauom usmemusmmma ucmumumap one .maxs Hmoauum> on» so pmuuon ma ch00 .mo>amo H adouu aw Ashpov wocmwamaoo oassshp do mum>bwcsa huwommmo Hmuw> use unassumfln mo nommmm v flmDQHm ’41 .V maze... .InTOm .Im10m .InTm. 2.52m... .9580 O o..- W V ...... w Om- 0 I! m ONT. 9 J om? in 0 6.25.5... 3.02.60 .2... 326' 6.25.3... 3.02.3 .2.» :23- #0 .Hm>wa mucsoaMHcmHm Ho. esp How cwumasoamo use when mouse pnmscmum .vmmmwo vs: scamsmsa mcaEsuma: seams nuances cm a mmlom .pwmmwo Us: scamsmca mafiamumfin Hmumm mmussafi on u mmlom .pmmmmo can scamsmcfl unassuman seams mmpscafi ma n mmlma onus: mwxu Hmucouwuon map so vmuuon one NUOflumm usmemusmsoa ucmuommav 039 .meM Hmoauuo> on» so newscam ma savu .mu>amo H edema aw .chvu. «usuaamaoo owasshv co muw>bocma huaommmo Hmuw> new unassumfln mo uomwwm w MMDQHW kl .Imnow .In.-Om w mmszm 1.79 2.52.... 6.28 11111 O o? 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U 1910M go we 46 Histamine increased P-V hysteresis (Fig. 7) and peak expiratory flow rates (PVEX) (Fig. 8) but these effects were significantly reduced by vital capacity maneuvers (table 2). .HebeH eOQMOHMHcmHm Ho. ecu How veustono ewe euec House onmucmum .vemeeo pec cOHesucH ecHamuMHc neume meuscHE om u mmloo .Uemmeo vec consmcH ecHEeuch Heume eeuscHE on a union .Uemmeo sec coHeawcH ecHaeueHc ueuwe meuscHa mH I mmImH euec3 eHxs HeucouHuoc ecu 7: .4 co peuuon ens mpowuem uceEeuSmeeE uceueMMHp ecB .eme HMUHuHe> ecu co Ueuuon eH mHeeueuemc >1m .ee>Heo H adouw CH .mHmeueumhc >Im. mumeueumhc eEsHo>Ieusmeeum co mue>secea muHoemmo Hmqu use con5wcH ecHEeuch mo uoemmm h MMDUHh 118 now .Imuom . u 6.. 6.52.6... 2.0.33 6.6.56.3... 3.02.3 K 3:5... 3.62mi .2... .3... .2... 6.82. 8E0 N4 0... 1010A! {a we 'soun 235.5»: .>un.. ‘19 .He>eH ecceonHcmHm Ho. ecu you veudeoHeo ens when uouue cueoceum .ceeeeo sec con5MCH eCHEeuch ueume eeuscaa cm H mmlow .uemeeo Umc cOHesmcH ecHseuMHc Heumm meuscwa on n mmnom .uemeeo sec conDMcH ecHEeuch ueume eeuscHE mH u mmImH euec3 mem HmucouHuoc ecu co veuuon ewe mooHHem uceaeusweee uceuemwwp ecB .mee HMUHuHe> ecu co peuuon eH .xm.¢m .wemeo H mnouo :H .xm>m. son auoumumee xeem so mue>decms muHommmo HmuH> use :onswcH eCHEmueHc mo uoemmm m mmDOHh 50 m 3.2.... .Imuom .Imuom .Idé. 9.33.6... .2633 .2... .23. 3252.6... 282.8 .23 0.22.- 8.82m... .2250 ON... om; 7 E '> o.- I /saw. 'mw 51 0.0m eCHseumHm NN.vw ecwsmumHm He>eH Ho. ecu um uceoHMHcmHe hHHeoHumHumum uoc eue esHH esem hc ceuooeueccs acme: d. n.6m m.mm s.~m v..m m.mn —.ms m.en H.ms 6.65 mmum. o> masseumum mmuoo Houucoo mmnom o> Houucoo o> sauce o> mmum. o> mmuom .css\uueuuH. .¢.m.m .c mo.h o..m wo.v hm.v m~.v -.m mo.n no.~ .v.~ mm m. xenon o> unusuumum :muoo Houucoo o> mmum. o> mmuom o> mmuom o> Houucoo 89. 5.333. 33.315.-. .o .ee>Hso H mdoum cH .>.w.m use eHeeueumac >Im you memes :ee3uec cOeHHemEoo HMUHumHumum N Manda 52 ii) Gas Exchange PaOZ decreased 38 mm Hg below control values, due to a 34 mm Hg rise in the (A-a) 02 difference (Fig. 9, table 3). Changes in PA02 and VD/VT were not significant. TABLE 3 Statistical comparison between means for Pa02 and (A-a) 02 differences in Group I calves. a. PaOZ (mm.Hg) Histamine 15-PH 30-PH 60-PH Control 28.7 52.8 63.2 65.3 66.6 b. (A-a) 02 Difference (mm.Hg) 60-PH 30-PH Control 15-PH Histamine 39.7 40.5 43.1 54.5 77.0 * Means underscored by same line are not statistically significant at the .01 level 53 .He>eH eoceonHcmHe Ho. ecu wow ceueHcoHeo ewe mwec wowwe ewecceum .ereeo vec cOHecmcH ecHEeuch weuue meuscHE om maloo .mewwu 063 COHmHuMGH Qfiaflumfifi Hwflmw mwubdfifi on N Emu-om .cemeeo vec conducH ecHEeuch weume meuccHE mH mmimH ewec3 eer Heucouwwoc ecu co ceuuon ewe eUOHwem uceaewsmeefi uceweuqu ecB .eer HeOHuwe> ecu co oeuuon ewe coweceu cemmxo HeHweuwe OHEeumhm use meocewemee cemmxo HeHweuwelweHoe>Hc .ee>Heo H msowm cH emcecexe eem co cowmsmcH ecHEeuch mo uoemmm m mmDUH .m Sh m mmDGH. 19.8 :38 {we 055.23: 3.18 . - q #1 H l_+-1 I 6.36:... .226... 5:3 3.3.2 0.3.1:... 62.6.3.5 5:3 .o..2.<-.o.oo>.< ON1 9'1 00... 004 '6” {a “mu! 55 iii) Cardiovascular Effects pf Histamine Cardiac output decreased by an average of 8.3 liters/min during histamine infusion, and did not significantly recover in the hour following the infusion (table 4a). The decrease in cardiac output was accompanied by a decrease in pulmonary artery pressure (Fig. 10, table 4b). Significant increases in pulmonary vascular resistance could only be demonstrated between “control" and ”GO-PH" mean values (table 4c). Mean systemic arterial pressure decreased by an average of 74 mm Hg during histamine infusion and failed to recover significantly over the following hour (Fig. 11, table 5a). Systemic vascular resistance did not change. Increases in heart rate occurred during histamine infusion, and were accompanied by corresponding decreases in stroke volume (Fig. 12, tdfleS). 56 TABLE 4 Statistical comparison between means for cardiac output, pulmonary artery pressure and pulmonary vascular resistance in group I calves. a) Cardiac Output (liters/min) 15-PH 60-PH Histamine 30-PH Control 4.99 5.38 5.42 5.63 13.70 b) Pulmonary Artery Pressure (mm Hg) Histamine 15-PH 30-PH 60-PH Control 19.8 23.8 28.2 30.0 30.6 9’ Pulmonary Vascular Resistance (mm Hg/Liter min'1) Control Histamine 15-PH 30-PH 60-PH 2.48 3.85 5.07 5.27 6.19 * Means underscored by same line are not statistically significant at the .01 level 57 uceEewSmeeE uceweMMHp ecB .mee Isuee> mwecOEHsm .usmuco oevaeU .He>eH eoceoHMHcmHm Ho. ecu wow UeueH§0Heo ewe ewec wowwe ewecceum .Ummwwo can flOdeMGH Oflfifidumfln kuwm mwflflcfifi om fl mmloo .vwmewo we: cOHmdeH OQHEMHMHS kume mwuflnfia cm H mmlom .eeeeeo eec cOHesmcH ecHseueHc weume meuccus mH u mmImH ewecs mee Heucounoc ecu co peuuon ewe mponem HeoHuwe> ecu co vequHm ewe ewdeeewm hweuwe hwecOEHsm oce eoceumHeew weH .ee>Heo H mcoww cH ewcueHsoee> mwecoEHsm co cOHMSMcH ecHEeuch mo uoemmm or mmDUHm 58 wmud nouw Monounnd '01.; [a mum EH8 .Iamom o. $25.... 1...... oc_Ec.m_I .8200 l J A 10. fl O ................... O 09:26.:m ‘ 6.366... d ,.ww'u4y/w-710'ww 0509331003 lounacoA houomund sndmo ”ng09 palm ' sum 59 .Hm>wa oocmoamwcmwm Ho. 0:» How Uwumadoamo mum mama uouum vumvcmum .cwmmwo can :oamsuca madamumfi: umpmn mousnaa om u mmuom .cmmomo can :ofimsmca measmumas umuum amusaaa on u mmnom .cwmmmo can scamsuaa measuumfin umumm amusaas ma n mmuma wumn3 mflxm Hmuconwuon «nu co omuuoam mum m60aumm ucwamusmmoa acoummwflc 0:9 .mwxw Havauno> 0:» co @0990am mum mufimmmum Hmwuwuuu oaamummm van mocmumwmmu MMHSUmM> oafimumww .uamuso omwvumo .mm>amo H adouo cw ouaumadomm> vasoumhm no cadmawcfl mcafiwuma: mo pommmm : NMDOHm 60 01000014 own“; '5” ’0 10m: : maze: {Mom :38 :39 055.5: .228 A L TON 6 0 row .00. l rON. 0. ...... .0 59.5 0. ............ 0 02.20.00: I Sana-t n 0 I 0.. a: ON. I I 0001003 00'0”“ 01005053 mm- °¢ um I'M I D 4 V o... O - A V o J! ndsno ”moo I-‘UIW ' '01!!! 61 .Hw>0H wocwofimacmam Ho. .cmmmmo no: coamsuaw .vmwmwo on: :omeMGH .ommmmo can :OHmamca 0:» now omumaaoawo mum mumn uouum cuwvcmum ocasdumwn umuuw mmusCHE om a mmsoo mcasmumfln Hmumm mwpscas on n mmlom mafismumfin Hmumm amuscwe ma u mmlma mums: mfixm Hmuconauon m£u co kuuoam mum mcowumm ucofiwusmmoe ucoumumwv 0:9 .mwxu HMOfluum> ms» :0 vmuuon mum mwanmwnu> cmHSmme mph .mw>amo H miouw ca mumu uuwmn new wESHo> mxouum .usmuao omwcumo co scamswca wcaawumw: mo uowmmm NF mmDOHm 62 NH mmstm :an £520: 280 .00 O ........ 025.9 2.2.» 1 20¢ 3.— 00; v wa'uwy Mm ammo 63 TABLE 5 Statistical comparison between means for systemic arterial pressure, heart rate and stroke volume in group I calves. a) Systemic Arterial Pressure (mm Hg) Histamine 1S-PH 30-PH 60-PH Control 41.4 54.6 63.0 69.2 115.4 b) Heart rate (beats/min) Control 30-PH 15-PH 60-PH Histamine 154.4 185.2 189.2 189.8 224.8 c) Stroke volume (ml) Histamine 60-PH 15-PH 30-PH Control 24.3 28.3 28.4 30.5 91.6 * Means underscored by same line are not statistically significant at the .01 level 64 Significant differences were found to exist between animals for the following variables: a) Pulmonary mechanics - Cstat' Cdyn! Raw, Ptp' PGEX’ PvHysteresis b) Gas exchange - VD/VT' PAOZ, (A—a)02 Difference c) Cardiovascular variables - Psyst.' Heart rate, Systemic vascular resistance iv) General Observations Calves died soon after removal from the ventilator despite resuming spontaneous respiration. At post-mortem, the small and large intestines were frequently distended with gas and fluid and the lungs failed to collapse completely. There was no gross evidence of atelectasis or pulmonary edema. v) Blood histamine levels Mean plasma histamine levels rose from an average of 5.3 ng/ml prior to histamine infusion to 196.9 ng/ml during histamine infusion. Histamine levels had fallen to an average of 11.1 ng/ml by one hour after cessation of histamine infusion. 65 B. Group E; Measurements were taken during seven periods, as indicated below. Studies were conducted on six calves. ”Control" - control measurement prior to H1 antagonist administration. ”H1 Block” - 15 minutes after the infusion of the H1 antagonist. "Lo Hist” - during infusion of a low dose of histamine diphosphate when steady state conditions were reached. ”Hi Hist” - during infusion of a high dose of histamine diphosphate when steady state conditions were reached. '15-PH”, ”BO-PH" and '60-PH” - measurement periods at 15, 30 and 60 minutes after the cessation of histamine infusion. Rapid injection of the H1 antagonist, Tripelennamine (5 mg/kg I/V) resulted in transient increases in resting and maximal FTP! and a biphasic decrease/increase systemic arterial pressure response. Spontaneous return to pre-injection values occurred within several minutes (Fig. 13). No observed changes in blood pressures or transpulmonary pressure occurred following subsequent rapid intravenous administration of the H1 agonist PEA (50 meg/kg). Histamine diphosphate was infused at a mean ”low dose rate” of 44.4 mcg/kg/min (range 42.0 to 52.9 mcg/kg/min). The average "high dose rate” was 88.6 mcg/kg/min (range 8401 to 10509 ng/kg/min). 66 .mwxm Hmucouwuo: on» so nouuoam ma cowuomhca “ovum mafia 0:9 .Amumv ousmmoum MMMCOEHsmmcmuu can Adam. mudmnmum humans mumCOEHdm .Aumhmmv musmmmum Ofiamumhm mum maxm Hmowuuw> wnu co omhmammaa .ocHEdscmammfluu .umflcommucm Pa 0:» mo msaon mdosobmuuca Gamma m cm>wm wamo m scum mcaomuu Housmma mp MMDUHW 67 mH manuHm .:o_.oo_:_ .0..u .0.==== w m w m m _ o n . . . . u u a: e omzé Em. g. :2 l n. .0: .EE O§M._f1!\/ cam omH ONTE » 50>:OCOE .mam. . n. szooaoo .o:> 633.3. 32325 .1 Ln... :3 So: 9:qu 68 i) Pulmonary Mechanics Infusion of the H1 antagonist produced no significant change in Cstat.' Cdynv PTPI P-V Hysteresis or Raw’ At approximately six times the dose of histamine used in Group I calves, histamine failed to produce significant changes in Cstat' Cdyn' FTP! or Raw“ Vital capacity maneuvers significantly reduced the P-V hysteresis, in both control and histamine infused calves. Unlike Group I calves, PVHysteresis values during histamine infusion after vital capacity maneuvers were signifi- cantly lower than control measurements (Figure 14, table 6). ii) Gas Exchange Paoz, (A-a)02 difference and VD/VT were not significantly affectd by either the H1 antagonist or histamine infusion. Small changes in PAOZ occurred (table 6b) but significant differences were only demonstrated between ”control" and post-histamine infusion measurement periods. These were associated with an increase of at least 6.5 mm Hg in PaCOZ, with the difference between “control” and ' 30-PH” values for PaCOZ found to be significant at the .01 level (table 6c). 69 .H0>oa cocoonmacmnm Ho. 0:» now omumasoamo mnd mnmn nonnm Unmocmum .owmmwo on: conm5msn mansmumwn nmumn nuances om u mmlom .ommmuo on: conmsman manamumns nmunu amuscns on u :mnom .owmmmo on: sonmsmcw mensmumfln nmumm nuances ma n manna ono£3 mdxm Handcudnon man so oouuon one moannmm unmamnsmmms uconwmmnc on» can wwxu Hmonunm> 0:» co omhcamnwv ma mnmonmumxn >Im .szobm Oman ma mnm>bmcma annommmo Hayfi> mo Hummus 0:9 .m0>amo HH adonw :4 Amfimmnmumhn >Imv mam nmnmum»: masao>nmnsmmmnm so smwcommusm Fm measoaaom oswsmumfin can .msflamccmammwnuv womxooan Fm mo noowwm v— ”8&3th 70 ea umzuHm In In. 8 on m. :9: 33 L. «.8522: £033 _2_> 8:6 I 23:82: £388 .23 283 w In. .EI .21 bxoom f .280 0.... T V 20/001 [0 we sou/7 285.5»: .>un._ 71 ao>0~ Ho. 0:» an usuonuacmuu haauodunnuuun no: and wean can. an vonooanoocn occur 0 h.cv o.ov v.0n m.hn n.6n h.wn m.nn 2.78 .3qu 57m. and. :3: x83 .= and. 03 .8330 3: E: «82. .0 mm.am on.mo hm.vm 00.no mm.—@ Nn.—o Nm.mm 33:8 and. 03 and. :3: good. .: gum. .818 .318 3: 3.: ~93 3 5N.v wh.n donucoo xOOam .2 omé .n.n a..." 8.“ Sun o..~ 3.... 8.. 2.. 2.. 3.. 3.. 2.3. an... :3... an... .38 us “5 2. u... as p33: gun... as... 03 as 3 x88 .2 .838 .3 on as 8 03 :3: .ONI l0..nu«av nanonouahn >Im .1 .00>~ao HH muonu .Nooum can ~onm nan 0:103 cooruon conundmaoo Haununnuuum o .AAIB 72 iii) Cardiovascular Effects There was no change in cardiac output during histamine infusion but, at the high dose rate, histamine halved systemic vascular resistance and decreased systemic arterial pressure by an average of 42 mm Hg (Fig. 15, table 7). Heart rate increased in all measurement periods subsequent to H1 antagonist administration (Table 8a). Changes in stroke volume were not significant. Decreased pulmonary vascular resistance following histamine infusion was accompanied by decreased pulmonary artery pressure (Fig. 16, table 8b). TABLE 7 Statistical comparison between means for systemic vascular resistance and systemic pressure, Group II calves. a) Systemic Vascular Resistance (mm Hg/Litre min“) High Low Hist Hist 15-PH 30-PH H1 Block 60-PH Cont. 5.50 5.64 8.28 9.39 10.51 10.86 11.31 b) Systemic Pressure (mm Hg) H1 Hist Lo Hist Cont. 15-PH 30-PH 60-PH H1 Block 78.3 91.7 110.7 111.3 118.5 120.0 121.7 * Means underscored by same line are not statistically significant at the .01 level 73 .am>wa monsonmnsmam Ho. man now wouuasoawo 0nd mnwn nonnw unmocmum .omwmou on: canmnmcfl mcnamumfin nouum moussdfi om n mmlom .vonmoo on: scamsmsn ocnfimumnn nmumm mmuscaa on u mmuom .ommmoo on: canm5msn unassumnn nmuum mmuacna ma u mmnma snags .mwxm Hansonwnon can so moonnwm newsmnSmmos ucmnowmnw on» can .wflxu Hmonun0> any so vmanammao 0nd oosmumwmwn nmaaomm> owsmumam can ondmmmnm onsoumam .mo>amo HH adono an onsumadomm> unamumhm so smacommusm pm mansoaaow mcdsmumwn can Assasuccwammanu. coaxOOHA Fm mo uoowum mp m¢DUHh 7h gwassxs '6/4 ww) ( ,-'u./w '34] 7/ '9000181803 JDII'IOSDA O w. ma mmszm .1; in. .1“. E: .2: .385 om on m. as... :3 623.23.. 3302:. £50....»m I .95» m2... e_EoEam . _o::oo 9.: (by ww) 'amssaJd ogwassfls 75 TABLE 8 Statistical comparison between means for heart rate, pulmonary vascular resistance and pulmonary artery pressure, Group II calves. a) Heart rate (beats/min) High Low Control H1 block 60-PH 30-PH 15-PH Hist Hist 165.0 189.8 194.2 195.0 202.6 228.0 234.5 b) Pulmonary Vascular Resistance (mm Hg/litre min") Lo Hist. Hi Hist 15-PH 30-PH 60-PH H1 Block Cont 1.71 1.97 2.28 2.56 2.74 3.15 3.45 c) Pulmonary Artery Pressure (mm Hg) Hi Hist Lo Hist 15-PH 60-PH 30-PH Cont. H1 Block 27.0 27.8 30.3 30.5 32.7 35.7 38.2 * Means underscored by same line are not statistically significant at the .01 level 76 .Hoboa oocoonmncmnm Ho. oz» now wouoasoaoo onm mnon nonno onovcoum .mouon omov uconom luau can no compass mos ocfisoumnn osau nonn3 no moodnom ucosonSmmos ouocmamov .umHm swam can .umnm 30A .oomuoo on: :OHnSMcH ocwsouonn nouns mouscdfi so u mmloo .oomuoo on: sowmsmnw ocwsmumwn nouum movssas on a union .oomooo can scamswcw ocnaoumwn nouns mounsfla ma u mmlma ono£3 mews Hmucouwno: on» so mooHnom usosonSmoos usonommno on» can .mnxm Hoonu Ino> on» so commammac ono oocoumwmon noasomu> hnmsosflsm can ondmmonm hnouno xndcosasm .mo>Hoo HH aflonw an onduoasomo> anocosasm so smacomouco pm mca3OHH0m osasoumws can Aosaauccoaomfinuv oomeOan pm «0 uoouwm or HMDUHW 77 '55! 'ww) 1/7 '0oumsgsaa Jolnosoa Mouowlnd 'U/LU '91 (I- .In. .In. in 0m 0m 9 6533a :23 4. 66:67.33... 33025 3 $5me .3: E... .385 :2: :3 f .228 TacoESu recasti O¢. (5H ww) 'amssaJd Maw) Mouowlnd 78 iv) General Observations Significant animal to animal variation was found in Group II calves in all variables measured. Unlike Group I calves, animals did not die when removed from the ventilator despite receiving over six times the dose of histamine as the first group. No lesions were observed on post- mortem. 79 C. Group 2 Histamine diphosphate was infused into six calves at an average dose rate of 11.9 mcg/kg/min (range 4.55 to 18.4 mcg/kg/min). Measurements of pulmonary mechanical, gas exchange and cardiovascular variables were performed during six periods designated as follows: “Control" - prior to administration of H2 antagonist. ”H2 Blocker" - 15 minutes after the rapid intravenous injection of metiamide (5 mg/kg). ”Hist“ - during histamine infusion, after steady state conditions had been reached. "15-PH, ”30-PH' and '60-PH" - 15, 30 and 60 minutes after cessation of histamine infusion. 1) Effect on Pulmonary Mechanics Histamine infusion caused a decrease of 30 ml/cm H20 in Gay“ (Fig 17, table 9). This effect was reversed by vital capacity maneuvers. Raw doubled during histamine infusion (Fig. 18). Vital capacity maneuvers failed to return Raw to control values. Increases in PTP (Fig. 19) and P-V Hysteresis (Fig. 20) caused by histamine, were reversed by vital capacity maneuvers. No significant changes occurred in Cstat‘ 80 .Ho>oa oocoowuflcmnm Ho. onu now woundsoaoo ono anon nonno onoosmum .cowm5mcn osasounan meanso unosonamooa n .umwm .Uomnoo 6o: scam—pug ofifioumflfi Hound nonficfifi om fl mmloo 0U$M$U UM: COHWfiMCfi Qfigumflg HOHHQ awn-.555 on " mmlcm .vommoo on: cowmsmcw ocnsmuman nouns noussws ma u mmlma onon: mnxo Housounnon on» so moownom ucosoHSmmos usonommwo onu can .mwxo Hoonuno> onu co oouuon on c»o.v .oouonunsaaw omad ono mno>bocua %u«oomoo Houw> mo muoommo osa .mo>aoo HHH adonw an Asaoov ooconamaoo onaosmo so emwcommuco mm usasoaaou oqasoumwn can Aooaaonuosv oomxooHn «a no uoommo one hr EDUHm 81 zoom Imom NH In 9 mmaon .311 .285 «I .2280 0?? 2 8 Ho>oH Ho. on» no ucoowmncmwm maaoowumwumum no: onm ocna oEMm ha Uonoomnoocs msooz 0 ~.~. a... mm.m sm.m mo.m mv.m .v.m ~m.~ ov.~ 6m.~ om.~ m~.~ umnm mmum. o> umnm mmuoo mmuom .ucoo goonm Na o> mmnm. o> mmuoo o> mmuom o> goonm mm o> ucoo .omm so .mmnunn. mnmmnmumss>um .6 mm.6. oo.o. os.¢ 6o.m mo.m .c.m «5.6 m~.m m~.m m~.m -.m .o.m umnm o>umnz mmnmn xoonm mmuom mmuom unoo o> mmuom o> xuonm m: o> mmum. o> mmuom o> ucoo m: .om: .so. mam .0 ~a.. .~.. mmo. «mo. .mo. one. who. see. «so. moo. 56o. coo. awn: o> umnm mmum. o> :m1m. o> :muoo o> mmuom canon mmuom o> xoonm mm xoonm N: o> ucoo .ucoo ..u:na nounnxomm 26. 3mm in m.so. «.6o. m.vo. ~..o. s.mm v.vm ~.vm m.~m m.om ..mm «.56 m.vm o> mmnm. o> mmuom o> .ucoo o> :muoo o> xoonm m: acoo sauce :muom xoonm mm o> awn: mmum. umnm .omz 56\ne. anuo .m .mo>aoo HHH moonm .mnmonoummn >Im can mum .3om .cxou now memos coosuon counnomsoo Hoowuowumum m EQFH. 83 .ao>oa oosoonMHcmHm no. on» now vouoasoaoo onm mnmn nonno onoocmum .conm5mca ocfieoumnn magnum ucosonsmoos n .umam .cwmmmo on: conmsoan manamumnn nmuwu amuscna so u amuse .oooooo on: denounce ocnsounan nouwo mounsaa on u mmnom .oomooo on: sowmsmsn ocnaduman noumm nouscaa ma mmlma onon3 maxu Handcunno: on» so moannom ucosonsmmos uconoumnv ozu can .mdxo Honda unob on» so wouu0am on 3mm .oouonumaaaa Oman onm mno>bocus huwoomoo Houn> mo muoommo onB .oo>aoo HHH adonw an Aammv oocoumwmon mosnflo so amficomouso mm msaaoHaOM oswsounan can .oofisowuofiv ovoxooHn Nm mo uoomuo one mp NMDUHW 811 m: $5on .9605 m: .2280 In... 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N... .1. w_.00 u.o>:oc62.>._ooaou .25 .024 I m. .4. 9.2523: 5.890 32> 2.28 H (Law 1911/ /OZH wa) M03 85 .Ho>oa oocoonunnmnm Ho. onn now oouoasoaoo ono anon nonno onoonoum .nonnSHQA onnsoumwn manndo ucosondmooa n .umflm .6omumo can conmsncn mangapunn noun. amuscna as u amuse .uwmmwo can conmsna. ocnaaumnn nmuum nuancna on u mmuom .oomooo can scamsusw oceaonmen nouns nousnfia ma u mmnma onon3 .mnxo HoncONnnon on» no moannom pcoaonzmoos unonoumao onu can .mdxm Hmonuno> on» no oouuon on mum .Uouonuoaaae Oman onm mnobboeos munoomoo Houa> mo mnoomwo one .mo>aoo HHH msonu an “mum. onSmnonm anonosasmmconu so smdcomouno Nm measoaaom onfiaoumwn can novesonuosv oomnooHn mm mo uoowmo one mp abounh 86 an Item Imon Ian. 6.2505! 5.0860 .2.) 8:4 £250.32 £2.30 .85 285 maze: so I .385 N... .2200 wt or C" (I V 87 .Hoboa oonooamnnmnm no. on» now wouoaaoaoo onm anon nonno unannoum .GOHmsmnw onasonman mannsv unosonsmoos u .umem 63.8 was .8332: 05933.. noun... 3.655 8 .513 .Uommoo can downsmcfi ondsoumen noumo mouacas on I mmlom .oonooo can :Onmsmcn ocdsoumnn nouwo mouscfia ma mmlma onon3 maxo Houcounnon on» no oceanom unosonnmoos unonoumav on» can .maxu Hooeuno> on» no vouuon on memonoumhn >1m .ooumnuoSHHn ooao ono mno>5o=os anaconda Honfi> mo muooumo one .oo>Hoo HHH adonw an .mnmonoumhn >1mv memononmhn ossao>tondmmonm so noncommuno mm mnwsoaaom onfismuman one novesonuoav ovonOOan am no poommo one om NMDme 88 Imom ImOm £252.02 £02.60 .23 8.3 £252.62 £62.60 .25 285 om mmstm .«m so 00 ._~:_m I. w... (oZHwa/WII) 0100:0105" A-d 89 ii) Effects 92 Gas Exchange Histamine decreased Pa02 by an average of 41 mm Hg below control values, with a concurrent increase in (A-a)02 difference of 44 mm Hg. (Fig. 21, table 10). No significant change in PA02 or VD/VT was found. TABLE 10 Statistical comparison between means for PaOz and (A-a)02 differences, group III calves. a) P302 (mm Hg) Hist. 60-PH 15-PH 30-PH Cont. 34.7 67.8 68.7 70.5 76.1 b) (A-a) 02 Difference (mm Hg) H2 Block Cont. 30-PH 60-PH 15-PH 36.9 38.3 45.0 45.2 46.8 HZ BlOCk 76.8 Hist. 81.3 * Means underscored by same line are not statistically significant at the .01 level 90 .Ho>oa oonmonuwcmnm no. on» n0m oouoadoamo ono mnon nonno onoocmum .sowmsmnn ocnsoumnn mannso unosonsmoos n .umnm .oomoou can :OHmsmnn oawsounan nonno mousces om mmlom .oommoo con nonmamsn ocneoumnn nonno nonscas on n melon .oommoo con conosmcd onnaoumnn nonno monsnns ma u mmlma onon3 .maxo Honconwnon onu so moonnom ucoaonsmoos unonoumno on» can .naxm Hooeuno> on» so oouuon ono ondmmonm Huwnouno oesoummm can .ooconommno «0 Aside .moosonoumao nomhxo Hunnounolnoaoo>an .mo>Hoo HHH adonw cw omconoxo mom no smncomouco mm mnH3OHH0u onesoumwn can nooesonuofiv ooonooHn «a mo nuoommo one pm HKDUHE 91 Hm 55w: .9806 E8 1%... In“... ......_I «.1 3.2.8 \ 0 No CE I 8:23.; «23.. 01.1.0 00. 6H LULU 92 iii Cardiovascular Effects Cardiac output and stroke volume were significantly lower at "60-PH" than at control levels but 'histamine'values were not significantly different from those of the “control” period (Fig. 22). Histamine did not change heart rate (Table 11). TABLE 11 Statistical comparison between means for cardiac output and stroke volume, group III calves. a) Cardiac Output (litres/min) 60-PH Histamine 30-PH 15-PH H2 Block Control 6.52 7.32 7.35 7.40 9.63 11.52 b) Stroke volume (ml.) 60-PH 30-PH Histamine 15-PH H2 Block Control 37.0 43.2 43.8 47.0 60.9 68.3 * Means underscored by same line are not statistically significant at the .01 level 93 .Ho>oH oucmoeuenmem no. on» now oouoaaoaoo ono anon nonno unaccoum .conmamcn onnaoumen mannao unosonsnuos u .umam .oomooo can cowmsmcd ocnsmumnn nonno mouscaa oo mmlom oflwmflwo U03 COHDHpMfl—fl OGflEMUMHS HOHMM Nmfififia OM nu mmlcm .oomooo own scansusw ocnsoumwn nonno nouscns ma mmlmH onon3 mnxm Hounonwnon on» so oceanom ucosonamoos unonomweo on» can .mexo Hoowuno> on» so wouuoam onm osfiao> oxonum 6cm usmuso oowvnoo .mo>Hoo HHH mfiono an ossao> oxonum can usmuso oowvnoo no smanououno an mcdsoHHow ocasoumen new novesoeuosv oomnooHn mm «o muoommo one NN HKDGHm 94 (7“!) amnloA axons IOOWP .--1.1:0. cr-eo SAL = s. 8 3 . ‘ v IS 442 Q l U 20‘- -L4 #2 Hist. :st 3de GOPH Blocker Control ( may 519/7) mama oogpma 22 FIGURE 95 Injection of the H2 antagonist had no significant effect on pulmonary or systemic arterial pressures and resistances. Systemic arterial pressure decreased by an average of 62 mm Hg from "control” upon histamine infusion and failed to recover to control levels even at '60-PH” (table 12). Although highly significant differences were obtained for systemic vascular resistance using the 2~way analysis of variance, these differences could not be demonstrated as significant using Tukey's w procedure. The largest difference between means was between “histamine" and 60-PH. A 10 mm Hg reduction in pulmonary artery pressure occurred during histamine infusion (table 12) without any significant change in pulmonary vascular resistance. TABLE 12 Statistical comparison between means for systemic arterial pressure and pulmonary artery pressure, group III calves. a) Systemic Arterial Pressure (mm Hg) Histamine 15-PH 30-PH 60-PH H2 Block Control 59.5 72.2 88.0 92.2 111.0 122.2 b) Pulmonary Artery Pressure (mm Hg) Histamine 15-PH 60-PH 30-PH Control H2 Block 23.5 27.2 29.0 32.0 32.8 33.2 * Means underscored by same line are not statistically significant at the .01 level 96 Histamine infusion elevated packed cell volume (PCV) and hemoglobin concentration (Hgb) and both remained significantly different from control values at “GO-PH” (Fig. 23, table 13). Significant differences in plasma total solids were also found. "Histamine” was not signifi- cantly different from the control group mean of 4.61 gm/100 ml. Mean total solids for the '15-PH' and '30-PH" periods were significantly reduced from the control group, and the '30-PH' group was also less than during histamine infusion (Table 13c). General Observations As in Group I calves, animals died shortly after removal from the ventilator and had similar lesions upon post mortem examination. Significant differences between animals existed for all variables, except systemic arterial pressure, PaOz, VD/VT and (A-a) 02 difference. 97 .Ho>oH oonoonunnmem Ho. onu new oonoasoaoo onm anon nonno onoocmum .c0nmswcw onasoumen mannso unosondmoos n .umnm .emmumo on: conmnnan mansuumnn nouns mmuscna on a sauce mmlcm .oomsoo own nanosmcw onnsoumwn nonno nouscas om mmlmH .oommoo can sennsmcn onnsmumwn nouns «ounces ma onon3 nexo Hansonnnon on» no oceanom ucoaonSmuoa unonoMMHv onu can .mexo Hmonuno> onu no Gounodm onm canumnunoo Icon nanoamoson was monaom Houon .>Um .mobaoo HHH msonw an noauonusoocoo :HnOHmoson can mUeHOm Hanan A>omv ossao> HHoo nonoom no smecomouno mm measoHHOH onesoumwn 6cm AoUeEMAUOEV ovoxooHn N: no mucoumo one MN mMDth 98 mm mmzwnm egg-m +5-8 .196» 5.9 .2: m: C) 0.. a... 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High Hist. lS-PH 30-pa 60-PH **PA02 100.0 93.6 95.4 94.7 91.9 91.2 89.8 Pa02 82.2 78.3 77.1 75.4 74.2 79.5 77.4 (A-a) 002 23.4 21.2 23.7 24.4 23.6 17.1 17.7 vD/vT 23.2 24.8 22.6 23.0 20.7 25.2 29.6 Cardiac Output 10.76 12.62 19.32 15.29 16.10 13.71 11.47 Stroke vol. 65.7 66.3 83.3 67.7 81.7 71.3 59.3 *‘Heart Rate 165.2 189.8 234.5 228.0 202.2 195.0 194.2 **p8y3t. 110.7 121.7 91.7 78.3 111.3 118.5 120.0 "Ppa 35.7 38.2 27.8 27.0 30.3 32.7 30.5 PVR. 3.45 3.15 1.71 1.97 2.28 2.56 2.74 **svn. 11.31 10.51 5.64 5.50 8.28 9.39 10.86 Units for variables are as listed for group I calves. ** Significant differences between means at the .01 level. 1&7 mm>a¢o H mfioum Mom vmumua an and Quandauo> How adds: I ++ H0>0H Ho. an undue cocsumn moocmuomuuc undowuwcmum to 6895053. anaconda Hunt; I o> + hh.H oa.m mh.a ch.N oa.~ om.n mm.H Hm.n hm.a hm.N mo.N 0h.m mm.H 5N.v rammuoumhw >1m C. ««.o oo.o om.o mm.o o¢.o« o«.o« oo.o ov.o« om.o m«.o« wo.o« v«.o« «6.6 ««.o« x6: mum mmo. who. mmo. who. doc. who. 05c. 50c. who. woe. who. wbc. 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