Tracheal responsiveness to histamine, PAF-acether and acetylcholine in normal and actively ovalbumin-sensitized guinea pigs

The contractile effects of histamine (His), PAF-acether (PAF) and acetylcholine (Ach) were analyzed in tracheal rings from normal and ovalbumin-sensitized (OAS) guinea pigs. Although maximal responses to all agonists were enhanced in preparations from OAS guinea pigs, only the EC50 of Ach was significantly decreased. Previous treatment with 1 micronM indomethacin (IND) or 10 micronM quinacrine (QUIN) markedly displaced the dose-response curves for Ach on OAS preparations to he left, whereas the EC50 of His was only increased by QUIN. PAF-responses, however, were completely abolished by IND in preparations from both senstized and unsensitized animals. These results indicate that ovalbumin sensitization significantly affects the tracheal response to Ach, His and PAF, an effect that appears to be mediated by arachidonic acd metabolites

Effect of PAF-acether on the reactivity of the isolated rat myometrium

In non-pregnant rat isolated uterine strips PAF-acether (1-1000 nM) produced contractile effects on 74% of the preparations tested which were concentration-dependent in 44% of the cases (EC50 = 28 nM). All the preparations tested exhibited contractile responses to either acetylcholine or potassium. PAF-acether was less potent on myometrial strips from pregnant animals (EC50 = 0.3 micronM) and was only effective on 24% of the preparations tested. A second contractile concentration-response curve was reproducible in only 14% of the preparations from non-pregnant rats (EC50 = 13 nM), whereas all strips from pregnant animals were completely refractory to a second challenge with PAF-acether. These results indicate that PAF-acether induces contraction of the isolated rat myometrium within the Ssame range of concentration at which it is active in other tissues

Gossypol affects the responsiveness of isolated rat myometrium and vas deferens

The effects of gossypol on responsiveness of both rat myometrium and vas deferens were analyzed. In myometrial strips, gossypol (1-30 micronM) produced rightward displacemtns of the cumulative concentration-response curves to acetylcholine, bradykinin and oxytocin, accompanied by reductions in maximal responses. Gossypol (30 micronM) also completely abolished the contractions induced by field stimulation of the rat vas deferens. The IC50 values for gossypol against agonist-uinduced myometrial contractions and field-stimulated vas deferens contractions were similar, ranging between 13 and 18 micronM. These results provide additional evidence that gossypol exerts a direct and irreversible inhibition of the contractility of both male and female reproductive organs