W. Bernauer

Radioimmunological determination of thromboxane release in cardiac anaphylaxis.

A sensitive and specific radioimmunoassay for thromboxane B2 were detected in perfusates of anaphylactic guinea pig hearts. Indomethacin decreased thromboxane B2 levels in the perfusates to below the detection limit of the radioimmunoassay and concomitantly delayed the onset of coronary vasoconstriction after antigenic challenge.

Prostaglandin, slow-reacting substance, and histamine release from anaphylactic guinea-pig hearts, and its pharmacological modification

SummaryProstaglandins (Pgs), slow-reacting substance of anaphylaxis (SRS-A), and histamine were released from anaphylactic isolated perfused guinea pig hearts. Pgs were to the greatest part of the F2α-type. PgE2 was found in traces only. Neither PgA2, nor the metabolites 13,14-dihydro-15-keto-PgF2α and 13,14-dihydro-15-keto-PgE2 were detected in the perfusates. Isoproterenol reduced the PgF2α output significantly. This effect was increased by the addition of theophylline. Propranolol did not reverse the effect of isoproterenol, but in a high concentration (5 μg/ml) reduced the PgF2α output for its own. Indomethacin completely abolished the anaphylactic prostaglandin release.The histamine liberation was significantly decreased only by the combination of isoproterenol and theophylline, and also by a high concentration of propranolol (5 μg/ml). In contrast to the Pg release, the anaphylactic SRS-A and histamine liberation was not abolished by indomethacin, but rather increased.The results are discussed in view of the possible role of the released substances in the functional events of cardiac anaphylaxis.

Release of prostaglandins, a prostaglandin metabolite, slow-reacting substance and histamine from anaphylactic lungs, and its modification by catecholamines

SummaryIn sensitized perfused guinea pig lungs antigen (ovalbumin) released prostaglandins (Pgs) F2α and E2, slow-reacting substance of anaphylaxis (SRS-A), and histamine. Furthermore, high amounts of the metabolite 15-keto-13,14-dihydro-PgF2α were found. Accordingly, perfusion of nonsensitized lungs with PgF2α and E2 resulted in extensive destruction of both substances. Simultaneously with the mediator release, very intense bronchospasm and pulmonary vascular constriction occurred.Administration of histamine in nonsensitized lungs resulted in Pg release.Isoproterenol as well as adrenaline prevented the anaphylactic mediator release, and concemitantly inhibited the spastic effects in the lungs. Propranolol reversed these actions of the catecholamines. Also indomethacin abolished the prostaglandin release, but increased the liberation of SRS-A.The findings are discussed in view of the contraregulatory function of adrenaline in anaphylaxis.

Pharmacological modification of thromboxane and prostaglandin release in cardiac anaphylaxis.

Isolated perfused sensitized guinea pig hearts release relatively large amounts of radioimmunologically measurable thromboxane B2 (TXB2) as well as smaller amounts of prostaglandin (PGs) after antigenic challenge. Using thin layer chromatography the major PG released was shown to cochromatograph with PGD2, while smaller amounts of immunoreactive PGF2alpha were found. The TX-synthetase inhibitor imidazole (100 microgram/ml) significantly decreased TXB2 release and simultaneously increased PG release during cardiac anaphylaxis. On the other hand, the beta-sympathomimetic drug isoproterenol decreased both TXB2 and PG release from the anaphylactic hearts. While isoproterenol significantly diminished anaphylactic coronary flow reduction, imidazole was without effect in this respect. PGD2 (0.5 microgram/min and 5.0 microgram/min) infused intraaortally into non-sensitized guinea pig hearts reduced coronary flow dose-dependently. These results are compatible with the view that release of TX and PGs might contribute to coronary flow reduction in cardiac anaphylaxis.

Antagonistic effects of α-adrenoceptor blocking agents on arrhythmias, enzyme release, and myocardial necrosis in isolated rat hearts with coronary occlusion and reperfusion

SummaryIn isolated perfused rat hearts reperfusion of the occluded left coronary artery led to arrhythmias, their severity depending on the duration of the foregoing period of myocardial ischaemia. Simultaneously, high activities of the myocardial enzyme creatine kinase (CK) were released into the perfusion fluid. Corynanthine, blocking mainly α1-adrenoceptors, and rauwolscine, blocking mainly α2-adrenoceptors, concentration-dependently antagonized the reperfusion-induced arrhythmias (3–30 μmol/l). The most severe kind of arrhythmia, i. e., ventricular fibrillation was completely prevented by 30 μmol/1 of either drug. Also arrhythmias occurring already during the period of coronary occlusion were antagonized, as tested with corynanthine. The β1-adrenoceptor blocking agent metoprolol (1, and 10 μmol/l) had no effect at all against reperfusion arrhythmias, and the mainly al-adrenoceptor stimulating agent phenylephrine markedly increased the severity of these rhythm disturbances. The release of creatine kinase during the coronary reperfusion was significantly decreased by corynanthine, while the effect of rauwolscine was smaller and non-significant. Phenylephrine markedly increased the enzyme leakage from the myocardium. In all hearts the extent of the ischaemic and necrotic areas was determined. The percentage of the previously ischaemic area found necrotic at the end of the reperfusion, depended on the duration of the coronary occlusion. Corynanthine in a highly significant way decreased the area of myocardial necrosis, an effect obtained to some extent also with rauwolscine. The findings suggest that a-adrenoceptor stimulation is involved in the genesis of arrhythmias and myocardial damage associated with myocardial ischaemia and reperfusion. Possible mechanisms of action of corynanthine and rauwolscine are discussed, especially in view of the interrelationship between α-adrenoceptors and slow calcium channels.

Release of 15-keto-13, 14-dihydro-thromboxane B2 and prostaglandin D2 during anaphylaxis as measured by radioimmunoassay

Summary1.A specific radioimmunoassy for 15-keto-13, 14-dihydro-thromboxane B2 was developed employing a polyvalent 125I-labelled tracer.2.Using the radioimmunoassay large amounts of immunoreactive 15-keto-13, 14-dihydro-thromboxane B2 were found in perfusates of anaphylactic guinea pig lungs, but not in perfusates of anaphylactic guinea pig hearts. On the other hand, both lungs and hearts released immunoreactive thromboxane B2 after challenge, lungs being, however, much more active.3.Using a radioimmunoassay for prostaglandin D2 variable amounts of this compound were detected in perfusates of anaphylactic guinea pig lungs.4.While the cyclo-oxygenase inhibitor indomethacin (1 μg/ml) abolished release of thromboxane B2, 15-keto-13, 14-dihydro-thromboxane B2 and prostaglandins from anaphylactic guinea pig lungs, the thromboxane synthetase inhibitor imidazole (100 μg/ml) was without significant effect.5.The results indicate that in anaphylactic guinea pig lungs, contrary to anaphylactic guinea pig hearts, a major fraction of the total thromboxane released into the perfusates is in the form of the biologically inactive 15-keto-13, 14-dihydro-thromboxane B2. On the other hand, prostaglandin D2, which can be formed enzymatically or non-enzymatically from the prostaglandin endoperoxide PGH2, might contribute to vascular and bronchial smooth muscle contraction observed in anaphylaxis.

Concerning the effect of the K+ channel blocking agent glibenclamide on ischaemic and reperfusion arrhythmias

Reports on effects of ATP-dependent K+ channel modulating drugs on ischaemia-induced cardiac arrhythmias have been scarce and contradictory. The channel blocking agent glibenclamide (glyburide) has been considered as an antiarrhythmic candidate, because it antagonizes the ischaemic K+ efflux and the shortening of the refractory period. In the present investigation its effects were tested, therefore, in rat hearts with coronary occlusion and reperfusion. In untreated hearts, tachyarrhythmias occurred during the reperfusion, and less pronounced during the coronary occlusion itself. Large amounts of adenosine and its degradation products were released during the coronary reperfusion, particularly from hearts which developed ventricular fibrillation. Glibenclamide (0.1 and 1.0 micromol/l perfusion fluid) neither antagonized the ischaemic nor the reperfusion arrhythmias. Ischaemic arrhythmias were even intensified. Also in control hearts without coronary occlusion, pro-arrhythmic effects of glibenclamide were observed. Furthermore, the coronary flow was considerably decreased by the drug, and the release of adenosine and its metabolites was significantly increased. Sodium nitroprusside antagonized the glibenclamide-induced decrease in the coronary flow, but did not prevent the arrhythmias. The Ca2+ channel blocking agent gallopamil increased the coronary flow, decreased the adenosine release, and antagonized the arrhythmias in hearts with and without glibenclamide. In conclusion, the present findings do not favour the idea of an antiarrhythmic effect of glibenclamide. Rather, some propensity to the occurrence of arrhythmias can be produced by the drug.

The effect of ethanol on arrhythmias and myocardial necrosis in rats with coronary occlusion and reperfusion.

Ethanol (1, 2 and 3 g/kg, intravenously) decreased the severity of the ischemic arrhythmias in rats with ligation of the left coronary artery and subsequent coronary reperfusion. Reperfusion arrhythmias occurring intensively after occlusion times of 5 and 15 min, respectively, were however not antagonized. Similar results were obtained in isolated perfused rat hearts with final concentrations of 4 and 6 mg ethanol/ml. In rats with reperfusion after 60 min of coronary occlusion, 2 g ethanol/kg significantly reduced the percentage of the ischemic area which underwent necrosis. Moreover, the increase in the wet weight/dry weight ratio of the lungs, as a measure of edema formation, was prevented. The ethanol effects are discussed in the light of present knowledge of the pathogenesis of arrhythmias and myocardial necrosis in experimental myocardial infarction.

Histaminasefreisetzung durch heparin und protamin beim meerschweinchen

Abstract Injections of heparin have been shown to provoke very strong histaminase activity in the plasma of guinea pigs, but not in other species so far tested (rat, rabbit, dog, hen, man). The activity is much stronger than in anaphylactic shock, when more than 50 IU/kg of heparin is given. Like the anaphylactic histaminase the heparin induced plasma histaminase comes from the liver. This has been demonstrated by injections of heparin in different sections of the cardiovascular system as well as by studies of the effect of heparin on the heart-lung-preparation and heart-lung-liver-preparation. The histaminase activity of the plasma is completely abolished by aminoguanidine. Protamine (as sulphate), too, has a strong histaminase liberating effect on the liver, 5 mg being as effective as 50 IU heparin. Protamine and heparin, on the other hand, neutralize each other when given simultaneously by two different intravenous routes. In this case the dose relationship is 1 mg protamine sulphate to 50 IU heparin.

The effect of β-adrenoceptor blocking agents on evolving myocardial necrosis in coronary ligated rats with and without reperfusion

SummaryThe left coronary artery of rats was ligated either permanently, or for a period of 40 or 60 min, with subsequent reperfusion. In experiments with permanent occlusion, the hearts were removed and investigated 5 h after the coronary ligation, or immediately after death in animals which died earlier. The hearts from the reperfusion experiments were investigated 60 min after reopening the occluded artery.The extent of the ischaemic and necrotic areas of the hearts was determined. A quantitative photometric method was developed, for this purpose, using “negative staining” with Evans blue for the ischaemic area, and “negative staining” with triphenyltetrazolium chloride for the necrotic area.In experiments in which ligation was permanent, the percentage of the ischaemic area which underwent necrosis increased with the time after coronary occlusion. In reperfusion experiments, myocardial necrosis was detected earlier than in experiments with permanent coronary ligation.The β-adrenoceptor blocking agents pindolol, propranolol, and metoprolol significantly decreased the percentage of necrosis in experiments with permanent ligation of the coronary artery. The most selective of the β-adrenoceptor blockers, i.e. metoprolol was tested in the reperfusion experiments. In these experiments, the amount of necrosis was also significantly decreased.