title: Endothelium-dependent relaxing effect of histamine on the isolated guinea-pig main pulmonary artery strips.
abstract: Contribution of endothelial cells (ECs) to the effects of histamine (HA) was investigated on the isolated guinea-pig main pulmonary artery (GPPA) strips precontracted with noradrenaline (NA). HA caused dose-dependent relaxation at the concentrations ranged between 10(-8) to 10(-6) M but produced a contraction when a relatively higher concentration (10(-5) M) was used in unrubbed strips. Cimetidine partially inhibited the relaxing effect of HA without altering its constrictive action. In rubbed strips, however, HA produced a dose-dependent contraction. The constrictive effect of HA in rubbed strips enhanced after addition of cimetidine to the incubation medium. HA elicited a concentration-dependent relaxation in both unrubbed and rubbed strips in the presence of mepyramine. Impromidine produced a relaxation in the strips with and without endothelium. These data was taken as an evidence indicating that HA caused a relaxation in the isolated GPPA strips, first causing the release of endothelium derived relaxing factor (EDRF) which is triggered by H1-receptors and secondly by the direct stimulation of H2-receptors.
mesh_terms: D000818:Animals; D002927:Cimetidine / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000502:physiology*; D005260:Female; D006168:Guinea Pigs; D006632:Histamine / Q000494:pharmacology*; D007093:Imidazoles / Q000494:pharmacology; D017446:Impromidine; D066298:In Vitro Techniques; D008297:Male; D009126:Muscle Relaxation / Q000187:drug effects; D011651:Pulmonary Artery / Q000187:drug effects; D011738:Pyrilamine / Q000494:pharmacology; D011970:Receptors, Histamine H2 / Q000502:physiology
chemical_list: D007093:Imidazoles; D011970:Receptors, Histamine H2; D002927:Cimetidine; D006632:Histamine; D017446:Impromidine; D011738:Pyrilamine