The influences of andrenotropic drugs and noradrenaline on the histamine release in cardiac anaphylaxis in vitro

Shedding of the coronary endothelial glycocalyx: effects of hypoxia/reoxygenation vs ischaemia/reperfusion

BACKGROUND

Vascular endothelium is covered by a glycocalyx. Damage to the glycocalyx after systemic inflammation or ischaemia/reperfusion contributes to increased vascular permeability and leucocyte adhesion. The underlying mechanisms leading to ischaemia/reperfusion-induced glycocalyx shedding are incompletely understood, in terms of lack of oxygen, absence of flow, or return of oxygen.

METHODS

Isolated guinea pig hearts perfused with Krebs-Henseleit buffer at 37°C underwent 20 min of either stopped-flow ischaemia or hypoxic perfusion with subsequent reperfusion/reoxygenation (n = 6 each). Hearts perfused with normoxic buffer served as time controls. Epicardial transudate was collected to assess coronary net fluid filtration, colloid extravasation, and histamine release by mast cells. Syndecan-1 and heparan sulphate were measured in coronary effluent, together with lactate, purines, and the release of mast-cell tryptase β. Additional hearts were perfusion-fixed to visualize the glycocalyx.

RESULTS

Both ischaemia and hypoxia with reperfusion/reoxygenation resulted in significant increases in net fluid filtration (P < 0.05) and release of syndecan-1 and heparan sulphate in coronary effluent. These effects were already seen with the onset of hypoxic perfusion. Histamine was released during hypoxia and reoxygenation and also reperfusion, as was tryptase β, and high concentrations of adenosine (>1 µmol litre⁻¹, hypoxia group) and inosine (> 7 µmol litre⁻¹, ischaemia group) were measured in effluent (P < 0.05). Damage to the coronary glycocalyx was evident upon electron microscopy.

CONCLUSIONS

Both ischaemic and hypoxic hypoxia initiate glycocalyx degradation, promoting an increase in permeability. A contributing mechanism could be purine-mediated degranulation of resident mast cells, with liberated tryptase β acting as potential 'sheddase'.

Relaxin induces mast cell inhibition and reduces ventricular arrhythmias in a swine model of acute myocardial infarction

Resident cardiac mast cells, located mainly around coronary vessels and in the right atrium close to the sinoatrial node, are the main repository of cardiac histamine. Inflammatory activation of cardiac mast cells, as occurs upon acute myocardial infarction, causes the release of histamine and prostanoids. These substances lead to severe tachyarrhythmias, cardiodepressive effects and coronary spasm, thus contributing to myocardial damage and early, lethal outcome. Relaxin, known to inhibit mast cell activation, has been recently validated as a cardiotropic hormone, being produced by the heart and acting on specific heart receptors. In this study, we report on a swine model of heart ischemia/reperfusion, currently used to test cardiotropic drugs, in which human recombinant relaxin (2.5 and 5 microg/kg b.w.), given at reperfusion upon a 30-min ischemia, markedly reduced cardiac injury as compared with the vehicle-treated animals. Evidence is provided that relaxin, at both the assayed doses, causes a clear-cut, significant reduction of plasma histamine, increase in cardiac histamine content and decrease in cardiac mast cell degranulation. This is accompanied by a reduction of oxidative cardiac tissue injury (assessed as tissue malondialdehyde) and of the occurrence of severe ventricular arrhythmias. In conclusion, this study provides further insight into the cardioprotective effects of relaxin, which also involve mast cell inhibition, and confirms the relevance of histamine in the pathophysiology of ischemia-reperfusion-induced cardiac injury and dysfunction. It also offers additional evidence for the potential therapeutic effects of relaxin in animal models of disease involving mast cell activation.

Cardiac anaphylaxis: pathophysiology and therapeutic perspectives

Cardiac anaphylaxis refers to the functional and metabolic changes in the heart caused by the anaphylactic release of histamine and vasoactive products of arachidonic acid cascade by mast cells and basophils. As in most type I hypersensitivity-based diseases, histamine plays a key role in the pathophysiology of cardiac anaphylaxis. In the heart, mast cell activation and histamine release are controlled by multiple endogenous mechanisms, including adrenergic neural control, histamine-dependent negative feedback operated through H2 receptors, and the endogenous generation of nitric oxide (NO) and carbon monoxide (CO). All these mechanisms can be targeted by substances that have revealed a clear-cut effect in blunting cardiac anaphylaxis in experimental animal models, and could be developed as potential, novel anti-anaphylactic drugs. In this article, we discuss new findings and significant trends related to this topic.

Some new functions of amine oxidases

Two contrasting topics are examined in this account: the protective actions of amine oxidases (AOs) resulting from the elimination and/or modulation of the levels of polyamines and some biogenic amines, such as histamine, in anaphylactic shock and the cell damaging effect of AOs catabolic products. Other functions of the plasma copper-containing amine oxidase are considered; namely the modification of some proteins by oxidation of their free amino groups, the auto-regulation of the catalytic activity of AOs, the protective effect against free radicals, and the regulation of K(+)-channels.

Protective effect of relaxin in cardiac anaphylaxis: involvement of the nitric oxide pathway

1 Relaxin (RLX) is a multifunctional hormone best known for its role in pregnancy and parturition, that has been also shown to influence coronary perfusion and mast cell activation through the generation of endogenous nitric oxide (NO). In this study we report on the effects of RLX on the biochemical and mechanical changes of ex vivo perfused hearts isolated from ovalbumin-sensitized guinea-pigs induced by challenge with the specific antigen. The possible involvement of NO in the RLX action has been also investigated. 2 A 30-min perfusion with RLX (30 ng ml(-1)) before ovalbumin challenge fully abated the positive chronotropic and inotropic effects evoked by anaphylactic reaction to the antigen. RLX also blunted the short-term coronary constriction following to antigen challenge. Conversely, perfusion with chemically inactivated RLX had no effect. 3 The release of histamine in the perfusate and the accumulation of calcium in heart tissue induced by antigen challenge were significantly decreased by RLX, while the amounts of nitrites in the perfusate were significantly increased, as were NO synthase activity and expression and cGMP levels in heart tissue. 4 These findings indicate that RLX has a protective effect in cardiac anaphylaxis which involves an up-regulation of the NO biosynthetic pathway.

A plant histaminase modulates cardiac anaphylactic response in guinea pig

The effect of a copper amine oxidase (histaminase) purified from the pea seedling as free or immobilized enzyme on the response to specific antigen was studied in isolated hearts from actively sensitized guinea pigs. In vitro challenge with the specific antigen of hearts from actively sensitized animals evokes a positive inotropic and chronotropic effect, a coronary constriction, followed by dilation and an increase in the amount of histamine and nitrites, the oxidation product of nitric oxide, in the perfusates. In the presence of both forms of histaminases, the positive inotropic and chronotropic responses as well as the coronary constriction and the release of histamine were fully blocked. The amount of nitrites, appearing in the perfusates when anaphylaxis is elicited in the presence of both forms of histaminases, is significantly increased, as well as nitric oxide synthase activity and cyclic GMP content in cardiac tissue, while cardiac calcium overload was significantly prevented. These observations demonstrate that the decrease in the anaphylactic release of histamine and the subsequent abatement of the cardiac response to antigen can be accounted for by the inactivation by histaminase of the released histamine and by a stimulation of endogenous nitric oxide production.

Haeme oxygenase-1 and cardiac anaphylaxis

1. Haeme oxygenase (HO) is an enzyme mainly localized in the smooth endoplasmic reticulum and involved in haeme degradation and in the generation of carbon monoxide (CO). Here we investigate (1) whether the inducible isoform of HO (HO-1) is expressed in the isolated heart of the guinea-pig and (2) the functional significance of HO-1 on the response to antigen in isolated hearts taken from actively sensitized guinea-pigs. 2. Both the HO-1 expression and activity are consistently increased in hearts from guinea-pigs pretreated with hemin, an HO-1 inducer (4 mg kg(-1) i.p., 18 h before antigen challenge). The administration of the HO-1 inhibitor zinc-protoporphyrin IX (ZnPP-IX, 50 micromol kg(-1), i.p., 6 h before hemin) abolished the increase of both the HO-1 expression and activity. 3. In vitro challenge with the specific antigen of hearts from actively sensitized animals evokes a positive inotropic and chronotropic effect, a coronary constriction followed by dilation and an increase in the amount of histamine in the perfusates. In hearts from hemin-pretreated animals, antigen challenge did not modify the heart rate and the force of contraction; the coronary outflow was significantly increased and a diminution of the release of histamine was observed. The patterns of cardiac anaphylaxis were fully restored in hearts from animals treated with ZnPP-IX 6 h before hemin. 4. In isolated hearts perfused with a Tyrode solution gassed with 100% CO for 5 min and successively reoxygenated, the response to antigen was similar to that observed in hearts from hemin-pretreated animals. 5. Pretreatment with hemin or the exposure to exogenous CO were linked to an increase in cardiac cyclic GMP levels and to a decrease of tissue Ca(2+) levels. 6. The study demonstrates that overexpression of HO-1 inhibits cardiac anaphylaxis through the generation of CO which, in turn, decreases the release of histamine through a cyclic GMP- and Ca(2+)-dependent mechanism.

Cardiotoxicity of histamine and the possible role of histamine in the arrhythmogenesis produced by certain antihistamines

Since 1990 it has repeatedly been reported that some histamine H1 receptor antagonists (e.g. terfenadine and astemizole) are able to produce ventricular arrhythmias (e.g. torsade de pointes) when they are given at dosages above the therapeutic range and/or administered together with cytochrome P-450 3A4 inhibitors, such as ketoconazole or erythromycin. Although the mechanism by which these arrhythmias are produced remains unclear, the recently reported ability of these drugs to block outward K+ currents has been suggested as the cause of their arrhythmogenic effects. Alternatively, we have observed that some H1 antihistamines, including terfenadine and astemizole, are able to release histamine from guinea-pig cardiac mast cells. Thus, we have proposed that the liberated histamine, acting through an H2 receptor-stimulating mechanism, can prolong the action potential duration and hence induce arrhythmogenic effects. This paper describes experimental observations supporting the hypothesis that some H1 antihistamines can induce severe cardiac arrhythmias via the local release of histamine.

Inotropic effects of histamine on developing chick heart: release of transmitters from autonomic nerve terminals

Inotropic effects of histamine were examined in isolated ventricular preparations from late embryonic and hatched chick hearts. In 19 day-old embryonic preparations, histamine had little effect on the contractile force. In preparations from 1 to 2 day-old hatched chick, histamine produced a transient decrease in contractile force followed by a sustained increase. The negative and positive responses were antagonized by atropine and propranolol, respectively, but not by histamine antagonists terfenadine, cimetidine or thioperamide. Acetylcholine produced positive inotropic responses in the embryo while negative responses were observed after hatching. In myocardium of hatched chicks, compound 48/80, which releases histamine from mast cells, produced a transient decrease in contractile force followed by a sustained increase with a similar magnitude and time course to the case of exogenously applied histamine. The negative and positive responses were inhibited by atropine and propranolol, respectively, but not by terfenadine, cimetidine or thioperamide, which was similar to the case with the responses to histamine. The present results suggest that histamine, either applied exogenously or released from myocardial store sites, produces negative and positive inotropic responses in hatched chick myocardium which are due to release of acetylcholine and norepinephrine, respectively, from autonomic nerve terminals.

Chronotropic and inotropic effects of histamine in developing chick heart: differential mechanisms before and after hatching

Chronotropic and inotropic effects of histamine were examined in isolated atrial and ventricular preparations from embryonic and hatched chicken hearts. Histamine produced positive chronotropic and inotropic responses both in embryonic and hatched hearts. The responses to histamine in middle embryonic myocardia, which were observed in the micromolar range, were antagonized by H2 antagonists but not by H1, H3 antagonists and propranolol. Isobutyl-methylxantine, an inhibitor of phosphodiesterase, produced a leftward shift of the concentration-response curve for the chronotropic effect of histamine in the embryo. The responses to histamine in myocardia from hatched chicks, which were observed in the milimolar range, appeared concurrently with the responses to tyramine during development and were antagonized by beta adrenoceptor antagonists but not by any of the histamine antagonists. The positive inotropic response to histamine in hatched ventricular preparations were greatly attenuated by reserpine pretreatment or in the presence of desipramine. Thus, we demonstrated that exogenously applied histamine produces positive chronotropic and inotropic responses in developing chicken hearts and that the mechanisms are different between embryonic and hatched chicks: direct action on H2 receptors in the embryonic heart and release of norepinephrine from sympathetic nerve terminals in hatched hearts.

A sensitive method for simultaneous determination of histamine and noradrenaline with high-performance liquid chromatography/electrochemistry

A simple and reliable high-performance liquid chromatographic method is described for the simultaneous determination of histamine (His), which cannot be directly oxidized, and noradrenaline (NA), which can be directly oxidized within the useful working potential range. The isoindole products formed by precolumn derivatization of His and NA with o-phthalaldehyde (OPA) and 2-mercaptoethanol (2-ME) yielded a linear relationship of detection between the electrochemical signal and the compound content to a minimum detectable limit of 50 pg (signal-to-noise ratio = 3:1) for both compounds at 0.5 nA of detector range. Without 2-ME, OPA derivatives of both His and NA were not detectable electrochemically at the oxidation potential range from 0 to + 1 V. Although the peak potential was +0.85 V for both His and NA, we used +0.7 V for both compounds to keep background noise minimal. The capacity factors of some electrochemically interfering compounds were also determined. The significance of OPA/2-ME derivative of NA is discussed relative to the direct oxidation of catecholamines. An example of a practical application of the method to the determination of His and NA in rat cardiac tissue is presented.

Evidence of an adriamycin binding site in the secretory granules of the mast cell

Adriamycin induced significant non-cytotoxic histamine release from rat peritoneal mast cells to which the drug showed a very high affinity. The relationship between adriamycin-induced exocytosis and its uptake by purified rat peritoneal mast cells was studied. Adriamycin induced histamine release and was highly concentrated in mast cells at 37 degrees C but not at 0 degrees C. However, if exocytosis was provoked by other secretagogues like compound 48/80, protamine, concanavalin A, and ionophore A23187, and cells were then treated with adriamycin at 0 degrees C, the concentrations of the antineoplastic drug significantly increased. Adriamycin binding to purified granular material was similar to that of intact cells treated at 37 degrees C, but was not modified by metabolic inhibitors, extremes of temperature (0 or 45 degrees C) or by the carboxylic ionophore monensin. On the contrary, sodium cromoglycate limited adriamycin binding to granular materials as well. In addition, sodium cromoglycate, but not monensin, displaced the antineoplastic drug from mast cells, even when added after adriamycin. We conclude that the high affinity of adriamycin for mast cells is ascribable to the externalization of a granular binding site, as a consequence of the exocytotic process. The experiments with sodium cromoglycate suggest that this binding site could be in common with the antiallergic drug.

Histamine attenuates the arrhythmogenic effects of norepinephrine in hearts of spontaneously hypertensive rats

A potential physiological role for cardiac histamine and its interaction with norepinephrine were investigated in isolated left ventricles from spontaneously hypertensive rats (SHR). Prior to drug administration, left ventricle-to-body weight ratios and spontaneous firing rates (beats per min) were significantly increased in SHR ventricles vs. age- and sex-matched controls (WKY). Also, action potential duration was significantly prolonged in SHR at all levels of repolarization. In all hearts, norepinephrine (10(-7)-10(-4) M) increased spontaneous rate and the percent incidence of arrhythmias. The H2-receptor antagonist cimetidine (10(-5) M) potentiated the rate and arrhythmogenic effects of norepinephrine in SHR and, to a lesser extent, in WKY preparations; propranolol (10(-6) M) reduced them. Histamine (10(-7) M) also inhibited the norepinephrine-induced increase in arrhythmias in SHR, but not in WKY. The attenuation of adrenergically induced rhythm disturbances by histamine and their potentiation by cimetidine in hypertensive hearts support the hypothesis that histamine plays a role as a postjunctional modulator of adrenoceptor function in a setting of hypertension and myocardial hypertrophy.

alpha-Fluoromethylhistidine decreases the histamine content of the rat right atrium under the influence of sympathetic activity

alpha-Fluoromethylhistidine (alpha-FMH; 65 mg/kg, i.p.), a specific inhibitor of histidine decarboxylase, significantly decreased the histamine content of the rat right atrium in a time-dependent manner; the maximal decrease of 22.2% was observed 4 h after injection. However, alpha-FMH had no significant effect on the histamine content of the left atrium or the ventricles. The alpha-FMH-induced decrease in the right atrial histamine content was not observed in rats pretreated with 6-hydroxydopamine (25 mg/kg, i.p.). Two i.p. injections of 10 and 5 mg/kg of propranolol and the cardioselective beta 1-adrenoceptor antagonist metoprolol almost completely inhibited the alpha-FMH-induced histamine decrease. On the other hand, phentolamine (10 mg/kg, i.p.) had no influence on the histamine-decreasing action of alpha-FMH. These results suggest that in the rat right atrium there is a histamine pool where a rapid turnover of histamine is maintained by normal sympathetic activity.

Anaphylactic reactions affecting the human heart

We have investigated a large number of patients, most of whom suffered from severe systemic anaphylactic or anaphylactoid reactions during the induction of anaesthesia; the term 'anaphylactoid' was restricted to patients who had no history of prior exposure. Cardiac dysrhythmia (including severe bradydysrhythmia), which was documented by electrocardiography, was one of the principal manifestations, and in one case there was evidence of myocardial ischemia as well.

Pathophysiological significance of the distribution of histamine receptor sub-types: a proposed dual role for histamine in inflammation and type I hypersensitivity reactions

The pathophysiological significance of histaminergic receptors located on the membranes of immunocompetent cells is reviewed. H2-receptor agonists decrease the immunological histamine release from isolated serosal mast cells and from isolated hearts taken from actively sensitised guinea-pigs. Histamine and H2-receptor agonists inhibit the generation of superoxide anion from human neutrophils activated by FMLP and by substance P. These observations lend further support to the hypothesis of an immunodepression exerted by the activation of H2-receptors, which can be converted to immunostimulation by treatment with H2-receptor antagonists.

Distribution of mast cells in human heart auricles and correlation with tissue histamine

The mast cell density, fixation and staining properties, as well as tissue histamine, were studied in the human heart right auricles of 28 patients with mild atrial or ventricular septal defect (ASD or VSD respectively). We have found that different modes of fixation did not change significantly the mast cell appearance and number as stained with pinacyanol erythrosinate. The mast cell density was 21294 +/- 2775 cells per mm3 tissue and the mean histamine content of the auricle was 900.7 +/- 63.9 ng/g wet tissue weight. A significant positive correlation was observed between mast cell counts and histamine content (r = 0.79, p = 0.001). Furthermore, our data suggest the existence of a non-mast cell pool of cardiac histamine in man.

The antianaphylactic action of histamine H2-receptor agonists in the guinea-pig isolated heart

The effects of histamine and of H1- and H2-receptor agonists on the response to specific antigen were studied in isolated hearts taken from actively sensitized guinea-pigs. Histamine and H2-receptor agonists (dimaprit, impromidine) dose-dependently decrease the positive chronotropic and inotropic effects, and the severity of arrhythmias evoked by the challenge of sensitized hearts with specific antigen. Nordimaprit and the selective H1-receptor agonist 2-pyridyl-ethyl-amine (2-PEA) did not modify the patterns of cardiac anaphylaxis. The positive inotropic and chronotropic responses of the isolated heart to exogenous histamine appear to be partly reduced in the presence of dimaprit. The H2-receptor agonists decrease the amount of histamine released during cardiac anaphylaxis which is increased by cimetidine, while nordimaprit and PEA were ineffective, indicating an inhibitory function afforded by H2-receptors in cardiac anaphylaxis.

Comparison of the response of mast cells in guinea-pig cardiac atria and ventricles

A comparison was made between collagenase-dispersed guinea-pig atrial and ventricular tissues. Heparin containing cells were stained with alcian blue at pH 2.2, and counted by an automated technique (Technicon H6000). The cells were challenged with the specific antigen (ovalbumin), with antisera to guinea-pig IgG (non-subclass specific), IgG1 and IgG2, and the calcium ionophore A23187. Histamine release was measured by an automated spectrofluorometric technique, and leukotriene C4 was measured by radioimmunoassay. All of the following parameters were higher in the atrial than in ventricular cells (mean ratio and SEM of atrial: ventricular mast cell parameters in parenthesis): Histamine content/g wet tissues (3.32 +/- 0.71:1) (p less than 0.05), Absolute mast cell number as a proportion of total cell count (3.75 +/- 1.64:1), Histamine release induced by antigen (significant in one out of four experiments), anti-IgG (significant in three out of four experiments), anti-IgG1 (significant in two out of four experiments), and anti-IgG2 (higher but not statistically significant). Ionophore A23187 gave an inconsistent histamine release pattern: significantly higher release from atria in five treatments (different concentrations in different experiments), and higher ventricular release in three. Significantly more leukotriene C4 was released by antigen and the ionophore A23187 (mean of 3-5 treatments), but not with anti-IgG.

Release of leukotrienes and histamine by the isolated anaphylactic heart

The purpose of this study was to demonstrate the ability of heart tissue to release the mediators of anaphylaxis after antigenic challenges. Guinea pigs were sensitized with ovalbumin. Hearts were excised, perfused in a langendorff apparatus, and challenged with a bolus injection of ovalbumin. Analysis of the perfusates demonstrated the presence of histamine as determined by radioenzymatic assay. Histamine release was observed to be maximum after 2 min (8 +/- 1 nmol) of perfusion, then decreased to baseline level. The heart also released LTB4, LTC4, LTD4, and LTE4 as determined by high performance liquid chromatography and bioassays. The release of LTC4 occurred rapidly, reaching maximum after 2 min (4.2 +/- 1 pmol) and then returned to baseline level. Although the release of LTD4 paralleled the release of LTC4, it reached a maximum after 5 min (7.7 +/- 2 pmol). LTE4 was detected after 10 min and was undetectable after 15 min. Maximum release of LTB4 was observed after 5-10 min (15 +/- 3 pmol) and was no longer detectable after 15 min. These results indicate that the isolated sensitized heart undergoing antigenic challenge releases leukotrienes and histamine suggesting the cardiac anaphylaxis might occur by the locally released mediators.

Modulation of the spontaneous histamine release by adrenergic and cholinergic drugs

Experiments have been reported on the possible modulation of the spontaneous histamine release by adrenergic and cholinergic drugs. Adrenergic drugs increase the spontaneous histamine release in vivo, and in neoplastic mast cells, in vitro. The mechanism of histamine release appears to be dependent upon the activation of alpha-adrenoceptors. Cholinergic drugs activate the release of histamine in many secretory processes in vivo; in vitro, acetylcholine is one of the most powerful histamine releasers in isolated purified rat mast cells. The release of histamine evoked by acetylcholine in rat mast cells is a calcium-requiring, temperature-dependent exocytosis. The physiological relationship of the sympathetic, parasympathetic and histamine-containing cells are discussed.

Cardiovascular effects of ranitidine and cimetidine during acute myocardial ischaemia in anaesthetized dogs

The effects of ranitidine and cimetidine on ventricular fibrillation threshold and haemodynamics were studied in pentobarbitone-anaesthetized dogs subjected to acute coronary artery ligation. These drugs did not significantly change the ventricular fibrillation threshold nor haemodynamics before coronary artery ligation, except for remarkable haemodynamic depression by ranitidine 1 mg/kg. Ligation of the left anterior descending coronary artery reduced the ventricular fibrillation threshold, decreased systemic and left ventricular pressures and myocardial contractility, and slightly increased heart rate. Pretreatment with ranitidine 0.25 or 1 mg/kg, or with cimetidine 2 mg/kg, significantly abolished the reductions in ventricular fibrillation threshold, but did not noticeably alter the haemodynamic changes. These findings further support the hypothesis that histamine release may contribute to the increased ventricular vulnerability resulting from acute myocardial ischaemia. However, the role of histamine in the haemodynamic responses to coronary artery ligation remains obscure.

Effect of in vivo antiestrogen pretreatment on rabbit atrial chronotropic response to histamine

The chronotropic response (delta rate) to histamine (1.4 to 18 X 10(-6) M) of isolated atria from antiestrogen (tamoxifen)-pretreated immature female rabbit was investigated. Tamoxifen treatment (1.0 and 10.0 mg/kg/day for 14 days) had no significant effect on the delta rate. The Rmax and D1/2max were not significantly different in the two tamoxifen-treated groups compared to the oil-treated (1.0 ml/kg/day for 14 days) control group. Cimetidine (2.8 X 10(-7) M) inhibited the delta rate to histamine in all groups: control, 27%; tamoxifen (1.0 mg/kg), 38%; and tamoxifen (10.0 mg/kg), 28%. Only the low dose of tamoxifen was found to be estrogenic (uterotropic). We conclude that tamoxifen pretreatment, both at estrogen-agonist and estrogen-antagonist doses, is without effect on atrial chronotropic response to histamine.

The effect of compound 48/80, substance P and pentagastrin on the isolated guinea pig atrium

It has been shown that histamine is present in guinea pig hearts. In the present work, the effect of some substances, known to liberate mast cell histamine, on the isolated guinea pig atria was studied. Compound 48/80 (100 micrograms/ml), pentagastrin (10(-6) M) and substance P (10(-5) M) were added 2-3 times to the isolated organs and the frequency of contractions was measured. At the end of experiments, the atria were examined histologically for mast cell degranulation. Compound 48/80 and pentagastrin increased the frequency of contractions of isolated atria. Substance P provoked a dose-dependent decrease of contraction frequency; this effect was diminished by atropine (10(-5) M). All three substances provoked pronounced degranulation of mast cells present in the atrium, the effect of substance P being significantly greater than the effects of the other two substances. It can be concluded that mast cells, present in guinea pig atrium, are sensitive to the histamine liberators used; histamine is released in quantities high enough to produce an effect.

Cardiac mast cells: partial purification of guinea-pig atrial mast cells and release from them of histamine and leukotriene C4 by immune and non-immune stimuli

The response of cardiac mast cells in enzymically dispersed guinea-pig atrial tissue to various immune and non-immune stimuli was studied. These cells were also partially purified by density-gradient centrifugation. The release of histamine, and in some experiments leukotriene C4, was measured. The cells responded strongly and consistently to the calcium ionophore A23187 but their response to other non-immune stimuli such as neuromuscular blockers and morphine (which are known to cause anaphylactoid reactions in human and other species) was relatively weak and inconsistent. Relatively weak responses were also obtained by immune stimuli in the following decreasing order: anti-IgG, antigen, histamine-releasing lymphokine and then the complement fragments C5a-desArg and C3a.

The release of histamine by parasympathetic stimulation in guinea-pig auricle and rat ileum

Two preparations, a segment of rat ileum and the vagally innerved guinea-pig auricles, have been used in an analysis of the responses to vagal or to electrical field stimulation. The responses to parasympathetic stimulation were depressed by atropine and by tetrodotoxin, and potentiated by eserine. Supramaximal stimulation (10-20 Hz) resulted in increased release of acetylcholine and histamine, both in rat ileum and guinea-pig auricles. The release of histamine after parasympathetic stimulation did not exhibit tachyphylaxis, and it was not reproduced by non-parasympathetic stimuli. In both preparations, atropine produced a significant, dose-related reduction of histamine measured in the bath fluid after stimulation, while eserine increased histamine output. A significant diminution of mast cell granules metachromasia was observed in guinea-pig auricles and in rat intestine after parasympathetic stimulation. The possibility is discussed that acetylcholine released by parasympathetic stimulation would in turn evoke the secretion of histamine from tissue mast cells.

Inhibition of anaphylactic histamine release in vitro by GABA

Inhibitory effect of GABA on anaphylactic histamine release in vitro is not mimicked by 2-aminoethansulphonic acid (taurine), an aminoacid unrelated to GABA neuro-transmission. Tetrodotoxin (TTX) 6 X 10(-7) M, a concentration known to block neuronal mechanism but not to modify muscle membrane and anaphylactic histamine release, strongly prevented the inhibition caused by GABA in the Schultz-Dale reaction and in anaphylactic histamine release. The inhibitory effect of GABA on anaphylactic reaction in vitro thus appears to be specific for this aminoacid and is neurogenic in nature, in that it requires integrity of neuronal mechanisms.

Isolation and properties of cardiac and other mast cells from the rat and guinea-pig

A method is described for the enzymic dispersion into their component cells of cardiac tissues from the rat and guinea-pig. The resulting suspensions contain ca. 1% free mast cells and exhibit a low spontaneous release of histamine. The reactivity of these cells towards a number of defined chemical histamine liberators is compared with that of other connective tissue mast cells from the same animals. The results obtained are discussed in terms of the general functional heterogeneity of mast cells from different locations.

Histamine release during an experimental coronary thrombosis in awake dog

Histamine is released into the systemic circulation during anaphylaxis, by drugs and surgical procedures. Studies in animal models have shown that released histamine is one of the major mediators of arrhythmia occurring during anaphylaxis or the administration of histamine-releasing drugs. The variations in plasma histamine levels in dogs with a subacute coronary thrombosis were investigated and the effects of dimaprit and cimetidine on the electrocardiographic consequence of this thrombosis and on histamine release were assessed. During the first day after the myocardial infarction a ventricular arrhythmia developed and plasma histamine levels were found significantly increased, returning to the basal values when the sinusal rhythm was restored. Dimaprit was able to decrease the number of ventricular extrasystoles and to modulate plasma histamine levels. The action of dimaprit on ECG was not reversed by pretreatment with cimetidine, which on the contrary was able to antagonize the decrease in plasma histamine concentrations induced by dimaprit perfusion.

Effects of exogenous prostaglandins on the release of leukotriene C4-like immunoreactivity and on coronary flow in indomethacin-treated anaphylactic guinea-pig hearts

It is known that both vasoconstrictor cyclooxygenase products and sulfidopeptide-containing leukotrienes (LT) contribute to the biphasic coronary constriction observed in isolated perfused anaphylactic guinea-pig hearts. We have now investigated the effects of the cyclooxygenase inhibitor indomethacin and of several exogenous prostaglandins (PG) on the release of LTC4-like immunoreactivity and on various symptoms of cardiac anaphylaxis. Indomethacin decreased basal coronary flow and delayed the onset of coronary vasoconstriction after antigenic challenge. Furthermore, indomethacin inhibited cardiac release of 6-keto-PGF1 alpha and thromboxane (TX) B2 and simultaneously enhanced the antigen-induced release of LTC4-like immunoreactivity significantly. Neither the vasodilators PGE2 and PGI2 nor the vasoconstrictors PGF2 alpha, PGD2 and 11,9-epoxymethano-PGH2, a compound with biological properties similar to TXA2, affected the anaphylactic release of immunoreactive LTC4 in the presence of indomethacin. These results suggest that the indomethacin-induced increase in LT release is not due to inhibition of synthesis of a cyclooxygenase product, which normally curbs anaphylactic release of immunoreactive LTC4. The indomethacin effect may rather be explained by diversion of arachidonic acid metabolism away from fatty acid cyclooxygenase towards the synthesis of lipoxygenase products. Although the various PG did not significantly affect cardiac release of LTC4-like immunoreactivity, they antagonized the anaphylactic coronary constriction. This antagonism may be due to direct effects of the PG on vascular smooth muscle tone as well as to indirect effects on the release of anaphylactic mediators not related to LT like histamine and platelet-activating factor.(ABSTRACT TRUNCATED AT 250 WORDS)

Release of histamine by sympathetic nerve stimulation in the guinea pig heart and modulation of adrenergic responses. A physiological role for cardiac histamine?

Histamine has been reported to attenuate adrenergic responses in cardiovascular tissues. In guinea pig atria preloaded with [3H]norepinephrine, histamine diminishes the field stimulation-induced efflux of radioactivity; this effect has been attributed to an inhibition of norepinephrine release from nerve endings. To assess the possible physiological relevance of these findings, we have reinvestigated the effects of histamine on cardiac sympathetic responses and on the release of endogenous norepinephrine in the guinea pig heart isolated with its intact sympathetic innervation. Heart rate, left ventricular contractile force, and perfusion pressure all increased with increasing frequencies of sympathetic nerve stimulation (2-8 Hz). Histamine (3 X 10(-8) to 3 X 10(-7) M) caused dose-dependent attenuation of the responses to sympathetic stimulation. The ability of histamine to modulate nerve stimulation-induced norepinephrine overflow into the coronary effluent was dependent on whether the heart had been preloaded with norepinephrine. Whereas histamine did not cause a significant reduction in nerve stimulation-induced norepinephrine overflow in hearts from untreated animals, histamine significantly reduced stimulation-induced norepinephrine overflow in hearts from guinea pigs that had been pretreated with norepinephrine before sacrifice. Histamine also attenuated the increases in left ventricular contractile force, perfusion pressure, and heart rate, which result from the intracardiac administration of norepinephrine (0.16-microgram bolus injection). In this respect, histamine was as effective as it was in inhibiting the responses elicited by nerve stimulation. Thus, in normal animals, the negative modulatory effect of histamine on adrenergic responses can be attributed largely, if not totally, to a postjunctional mechanism. In contrast, a prejunctional action of histamine may contribute significantly to the negative modulation observed in norepinephrine-preloaded hearts. Since we have observed a large increase in the amount of endogenous histamine present in the coronary effluent after sympathetic stimulation (930 pg during the 30 seconds poststimulation vs. 240 pg during 30 seconds prestimulation), as well as a prolongation of nerve stimulation-induced cardiac responses in the presence of the H2 receptor antagonist tiotidine, we postulate that histamine plays a physiological role as a modulator of sympathetic responses in the heart.

Influence of GABA on anaphylactic histamine release in vitro

In this preliminary report an unreported inhibitory action of GABA on anaphylactic reaction has been described. In a functional model (Schultz-Dale reaction) GABA has been demonstrated to inhibit the antigen-evoked contraction. This effect depends on a modulation of anaphylactic histamine release. The phenomenon is dose-dependent and requires a period of time to develop. Since GABAergic neurons are present in the preparation, it is possible to speculate that GABA receptors are involved in this inhibitory action. However, pharmacological analysis of the phenomenon has to be carried out, especially in view of the latency of GABA to develop its effect.

Effect of inhibition of synthesis and receptor antagonism of SRS-A in cardiac anaphylaxis

The effects of infusions of the lipoxygenase inhibitor nordihydroguaiaretic acid (NDGA, 1.1 X 10(-7) mol min-1) and the antagonist of slow-reacting substance of anaphylaxis (SRS-A) FPL 55712 (1.2 X 10(-7) mol min-1) on the coronary constriction and the release of SRS-A, leukotreine C4-like immunoreactivity, thromboxane B2 and 6-keto-prostaglandin F1 alpha from perfused anaphylactic guinea-pig hearts were investigated. Both NDGA and FPL 55712 in the concentrations used induced an increase in basal coronary flow, but did not prevent the coronary flow reduction in the early phase (0-4 min) after antigen injection. On the other hand, NDGA and FPL 55712 inhibited the less pronounced long-lasting coronary flow reduction in the later phase of cardiac anaphylaxis. NDGA decreased the release of SRS-A from the anaphylactic guinea-pig hearts below or close to the detection limit of the bioassay and simultaneously diminished the release of leukotriene C4-like immunoreactivity. On the other hand, FPL 55712 did not influence the amounts of leukotriene C4-like immunoreactivity released in cardiac anaphylaxis. Neither NDGA nor FPL 55712 affected the release of immunoreactive thromboxane B2 (TXB2) from anaphylactic guinea-pig hearts. Release of 6-keto-prostaglandin F1 alpha after challenge, however, was decreased by NDGA, while FPL 55712 had no significant effect. These results suggest, that SRS-A may be a relatively more important mediator in the late phase of coronary constriction occurring during cardiac anaphylaxis, while the effects of other mediators, particularly vasoconstrictor cyclo-oxygenase products, seem to prevail in the early phase.

Effects of leukotrienes C4 and D4 on guinea-pig heart and the participation of SRS-A in the manifestations of guinea-pig cardiac anaphylaxis

Synthetic leukotrienes C4 and D4 (LTC and LTD) were found to possess potent coronary vasoconstrictor and cardiac depressant actions on isolated guinea-pig hearts. We therefore went further to investigate the possibility that endogenously released slow-reacting substance of anaphylaxis (SRS-A) might be responsible for the coronary vasoconstriction and negative inotropism in guinea-pig cardiac anaphylaxis. Results using time-course analysis as well as the specific SRS antagonist FPL 55712 have shown that SRS-A released during cardiac anaphylaxis was unlikely to be responsible for the early and most dramatic phase of coronary vasoconstriction that usually occurred at the 2nd min after antigen challenge, but could possibly be responsible for the latter and more prolonged phase occurring between the 6th and 14th min. This is because SRS-A release was found to peak at the 4th min after antigen challenge, 2 min after vasoconstriction had already peaked. Moreover, this early component of coronary vasoconstriction could not be blocked by FPL 55712, whereas the latter component was significantly reduced by the antagonist. The negative inotropism following cardiac anaphylaxis was also found to be significantly reduced by FPL 55712, thus suggesting SRS-A involvement. However, our experiments did not show whether the two actions were direct effects of SRS-A or whether contractility failure was a consequence of coronary vasoconstriction.

Polyamine levels and diamine oxidase activity in hypertrophic heart of spontaneously hypertensive rats and of rats treated with isoproterenol

Polyamine levels and diamine oxidase (EC 1.4.3.6) activity were studied in hypertrophic heart of spontaneously hypertensive rats as well as in the heart of Wistar rats during the development and regression of cardiac hypertrophy induced by isoproterenol administration. In spontaneously hypertensive rats, putrescine content and diamine oxidase activity were higher than those found in normotensive Kyoto-Wistar control rats. During the development of cardiac hypertrophy induced by isoproterenol, there was an increase in polyamine content and diamine oxidase activity. The administration of cycloheximide or actinomycin D prevented the increase in diamine oxidase activity during the first 24 h after isoproterenol administration, demonstrating that the rise in diamine oxidase activity was due to synthesis of new enzyme. Following the cessation of isoproterenol treatment, cardiac hypertrophy regressed and polyamine levels and diamine oxidase activity diminished toward control values. The administration of aminoguanidine to isoproterenol-treated rats caused in the heart an inhibition of diamine oxidase activity that led to an increase in putrescine level beyond the values found in animals given isoproterenol alone. The results suggest that the enhancement of diamine oxidase activity plays a role in the regulation of putrescine level in hypertrophic heart.

Protective effects of glucagon during the anaphylactic response in guinea-pig isolated heart

1 Cardiac anaphylaxis and the effects of glucagon pretreatment were studied in guinea-pig isolated hearts actively sensitized to ovalbumin.2 Antigen challenge of the sensitized hearts markedly increased creatine phosphokinase (CPK) activity in the coronary venous effluent. Control values of CPK release from the hearts before challenge were 3.56 +/- 0.15 mu min(-1) mg(-1). In the first 10 min following challenge, CPK release remained stable at increased levels which ranged between 4.88 +/- 0.20 to 5.39 +/- 0.38 mu min(-1) mg(-1). There was no correlation between immunologically released histamine and CPK release.3 Pretreatment of the hearts with glucagon (0.15 mumol l(-1)) exerted a pronounced anti-arrhythmic activity, reducing the conduction arrhythmias and completely preventing automaticity arrhythmias which normally occurred following ovalbumin challenge.4 Anaphylactic histamine release was reduced significantly in the presence of glucagon. The percentage inhibition of histamine release from glucagon pretreated hearts, during the first 10 min after challenge, ranged between 58% and 94% of that from hearts similarly challenged in the absence of glucagon.5 Glucagon significantly elevated sinoatrial nodal automaticity, enhanced atrioventricular conduction, improved coronary flow and reduced contractile force during anaphylaxis. It appears that these effects are caused both by modulating anaphylactic histamine release and by influencing the effects of the released histamine.6 CPK release from the anaphylactic hearts was significantly inhibited in the presence of glucagon. The average percentage inhibition of CPK activity during the first 10 min after challenge ranged between 42% and 98%.7 The findings from this study provide experimental evidence for protective effects of glucagon pretreatment during cardiac anaphylaxis.

The actions of leukotrienes C4 and D4 on guinea-pig isolated hearts

1 Infusions of leukotrienes C4 (LTC4) and LTD4 (5 min; 4 X 10-10-2 X 10-8 M) produced dose-dependent decreases in coronary flow in Langendorff preparations of guinea-pig isolated heats. 2 LTC 4 was more active than LTD4 and produced greater reduction in coronary flow 3 LTC4 and LTD4 also caused reduction in contractility in perfused hearts but not in isolated atria or driven ventricular strips. 4 There was a greater reduction in contractility to LTD4 compared with LTC4 at doses which produced approximately 50% reduction in coronary flow. 5 Indomethacin (1.4 X 10-5 M) inhibited the effects of LTC4 but only reduced the initial LTD4- induced effects. 6 The effects of FPL 55712 (3.8 X 10-6 M) were similar to those of indomethacin. 7 LTC4 and LTD4 may therefore contribute to the abnormalities of cardiac function that occur in immediate hypersensitivity reactions, particularly reduction in coronary flow.

Effects of histamine on the resting and stimulation-induced release of [3H]-noradrenaline in guinea-pig isolated atria

1 The sympathetic transmitter stores of guinea-pig isolated atria were labelled with [3H]-noradrenaline. The effects of histamine (0.3 to 100 mumol/l) on resting and stimulation-induced (S-I, 2 Hz for 10 s) release of radioactivity were investigated. 2 Histamine, in low concentrations (0.3 and 1 mumol/l) had no effect on resting release but inhibited S-I release of radioactivity. The inhibition was abolished by the H2-receptor antagonist, cimetidine (10 mumol/l) and also by the H1-receptor antagonist, mepyramine (1 mumol/l). 3 The inhibitory actions of histamine on S-I release were not due to indirect effects involving alpha-adrenoceptors, beta-adrenoceptors, muscarinic cholinoceptors or prostaglandin synthesis. 4 Histamine in a high concentration (100 mumol/l) increased the resting and S-I release of radioactivity. The increase in resting release was abolished by the neuronal uptake blocking drug cocaine (30 mumol/l) but the increase in S-I release was only partially blocked by cocaine.

Histamine release from human right atrium

Histamine release has been detected biologically after exposure of human right atrial biopsy samples to compound 48/80. Human right atrial samples contain large quantities of histamine, 1035 +/- 65 ng/g fresh weight. Exposure of untreated electrically paced atrial strips to compound 84/80, 300 micro/ml, caused an increase in the force of atrial contraction similar to that caused by histamine. Pretreatment of strips with cimetidine, 3.16 x 10(-5) M, prevented the inotropic response to compound 48/80. It is concluded that mast cell degranulation in human atrial tissue can cause sufficient release of histamine to modify the function of the heart.

Characteristics of histamine release evoked by acetylcholine in isolated rat mast cells

1. Histamine secretion from rat mast cells occurs in the presence of nanomolar concentrations of acetylcholine. 2. Intact glycolytic and oxidative metabolism is required for the acetylcholine-induced histamine secretion. Removal of extracellular glucose, hypoxia, cyanide and monoiodoacetate almost completely inhibit the secretion. 3. The secretion of histamine is dependent on the extracellular H ion concentration and is blocked when the cells are exposed to Na-deficient media. 4. The order of potency of cholinrgic agonists in evoking the secretion of histamine is oxotremorine > acetylcholine > choline > carbamycholine > nicotine. 5. Atropine competitively blocks the acetylcholine-induced histamine secretion, indicating the presence of cholinergic muscarinic receptors on mast cells. 6. Dibutyryl cyclic AMP and adrenaline inhibit the acetylcholine-induced histamine secretion, indicating a regulatory function afforded by cyclic nucleotides in the cholinergic histamine release.

Effect of ergometrine on contractile force of guinea-pig isolated heart: antagonism by cimetidine

The action of ergometrine on contractile force of guinea-pig isolated heart was investigated and the effect of receptor antagonists on the inotropic effect of ergometrine, isoproterenol, dopamine and histamine was evaluated. Ergometrine was found to have a good dose-dependent inotropic effect and the antagonism of cimetidine toward this action is reported. Experiments carried out in hearts in which a massive depletion of mast-cells histamine was produced are in favour of a direct action of the drug on H2-receptors.

Effects of guanethidine on histamine release during reflex vasodilatation in the dog

1 The effects of guanethidine pretreatment on the release of [14C]-histamine during the reflex vasodilatation induced in the atropinized gracilis muscle by rapid intravenous administration of noradrenaline, were studied in dogs. 2 After guanethidine treatment the haemodynamic reflex response was completely abolished and no appreciable modification of [14C]-histamine release from the gracilis muscle following intravenous noradrenaline was observed. 3 These results suggest the hypothesis that the withdrawal of the sympathetic discharge represents the mechanism of histamine release during the reflex vasodilatation. Therefore, guanethidine would suppress both the passive and the histaminergic component of the baroreceptor reflex through the abolition of the sympathetic tone.