Catecholamine release during anaphylactic shock in guinea pigs

On the mechanism of histamine-induced bronchodilation in conscious guinea-pigs

The bronchodilatory effect of histamine was evaluated in a conscious guinea-pig model of cholinergically mediated bronchoconstriction. The H1, bronchoconstrictor, property of histamine was masked using high doses of the H1-antagonist chlorpheniramine (30 mg/kg), and the bronchodilatory activity evaluated by observing the increase in latency to collapse induced by aerosol methacholine. Under these conditions, histamine (1.0, 3.0 or 10.0 mg/kg, i.p.) delayed methacholine-induced collapse in a dose-dependent manner. Cimetidine, an H2-receptor antagonist (10 to 100 mg/kg), did not delay collapse either in the presence or absence of an H1-antagonist. However, when cimetidine was administered prior to histamine, the bronchodilatory activity of histamine was abolished. A similar abolition of histamine bronchodilation was observed if propranolol, a beta-adrenoceptor antagonist, was administered prior to histamine. Propranolol alone had no effect on methacholine-induced bronchospasm. These data suggest that the major bronchodilatory property of histamine may be mediated indirectly via catecholamine release through an H2-receptor mechanism.

Physiological consequences of beta-adrenoceptor desensitization in guinea pigs

The effects of repetitive doses of beta-adrenoceptor stimulants on the resting tone and responsiveness of bronchopulmonary smooth muscle were studied in guinea pigs. Collapse time was used to assess bronchospasm in conscious animals while resistance and compliance measurements were used in the anesthetized guinea pigs. Repetitive administration of either isoproterenol or salbutamol, at effective bronchodilator doses, caused an exacerbation of the histamine-induced bronchospasm in the presence or absence of anesthesia. Repetitive administration of either prostaglandin E1, 20 micrograms/kg i.m., or aminophylline, 400 micrograms/kg i.m. did not enhance histamine-induced bronchospasm. Furthermore, in guinea pigs preselected for lack of histamine sensitivity, treatment with salbutamol caused a decrease in both dynamic compliance values and peak expiratory flow rate as well as an increase in resistance values. Trachea removed from guinea pigs treated with isoproterenol or salbutamol retained normal responsiveness to histamine and dibutyryl cAMP while the responsiveness to isoproterenol was reduced. These studies indicate that repetitive administration of beta-adrenoceptor stimulants can produce a specific desensitization of beta-adrenoceptors in pulmonary tissue and an alteration of resting baseline values of pulmonary mechanics measurements.

Release of creatine kinase by antigen, histamine, and catecholamines

In mepyramine treated, ovalbumin sensitized anaesthetized guinea pigs protracted anaphylactic shock was produced by i.p. injection of antigen, and serum creatine kinase (CK) activities were determined 4, 6, or 17 hrs thereafter. Significant increases above nonsensitized controls were obtained. In nonanaesthetized guinea pigs shock course and serum CK increase were considerably accelerated. Histamine increased the serum CK only when given in high amounts (10 mg/kg) s.c., in the presence or absence of mepyramine. I.p. injection of histamine in mepyramine treated animals had no effect. Adrenaline (1 or 10 mg/kg) given as a s.c. depot in oil produced a significant increase of serum CK, as well as noradrenaline (0.1, 1, or 10 mg/kg). Dibenamine reduced the effect of adrenaline. In isolated perfused guinea pig hearts a significant CK liberation occurred already within the first hour after eliciting anaphylaxis. Nonanaphylactic hearts released CK too, but significant amounts were obtained only in the total 4 hrs after ovalbumin administration. Isolated anaphylactic hearts incubated in Tyrode solution liberated significantly more CK than did nonsensitized control hearts. The findings are discussed in view of a possible myocardial damage in anaphylaxis.

Myocardial damage during protracted anaphylactic shock in guinea pigs

In ovalbumin-sensitized, mepyramine-treated guinea pigs protracted anaphylactic shock was elicited by i.v. injection of antigen. Diffuse or focal necrosis of myocardial cells was found in animals which died in protracted shock, as well as perivascular and interstitial edema. The antigen effects could be partially imitated by i.v. infusion of high amounts of adrenaline into nonsensitized guinea pigs. When adrenaline was infused during protracted anaphylactic shock, the catecholamine effects did not add to the histological effects of the antigen. Rather, the morphological alterations in the hearts were reduced, whereas the survival times were not increased, but decreased. - The findings are discussed in view of the nature of protracted anaphylactic shock.

The relationship between prostaglandin release and lung c-AMP levels during anaphylaxis in the guinea-pig

A four-fold transient rise in c-AMP levels was seen when sensitized guinea-pig lungs were challenged with antigen in vitro. This rise in c-AMP also occurred in vivo and was shown to be due to release of Prostaglandin E2. This conclusion is supported by the finding that inhibitors of prostaglandin synthesis (Indomethacin and Poly phloretin phosphate) prevent the rise in c-AMP while neither ICI 74, 917, an inhibitor of histamine release, nor antihistamines had any effect on the c-AMP levels.