Vasomotor effect of histamine on pig and cattle coronary artery in vitro.
Vasomotor effects of histamine were examined in isolated coronary arteries from pigs and cattle. Histamine produced a concentration-dependent contraction in these arteries. These contractile responses were dose-dependently inhibited by diphenhydramine. The slopes of the Schild plots, however, were significantly lower than unity in both species. Cimetidine potentiated the histamine-induced contractions at relatively high doses of histamine (larger than 10(-5) M) in pig coronary arteries, but did not show a significant effect in cattle arteries. After the removal of endothelium, the Schild plot of diphenhydramine against histamine gave a straight line with a pA2 value of 7.80 and slope of 1.00 in pigs, confirming the competitive nature of the antagonism. In cattle, the slope was significantly lower than unity; however, in the presence of cimetidine, it was not significantly different from unity. Dimaprit did not contract the cattle coronary arteries with endothelium, but contracted them after the removal of endothelium. These results suggest that histamine-induced vasoconstriction in pig and cattle coronary arteries is mainly dependent on the H1-receptors in the smooth muscle cells, and that H1- and H2-receptors in the endothelial cells of pigs and H2-receptors in the smooth muscle cells of cattle modify the histamine-induced vasoconstrictions.
Obi
T
T
Department of Veterinary Pharmacology, Faculty of Agriculture, Kagoshima University, Japan.
Matsumoto
M
M
Nishio
A
A
D000818:Animals; D002417:Cattle; D002927:Cimetidine / Q000494:pharmacology; D003331:Coronary Vessels / Q000187:drug effects*; D017259:Dimaprit; D004155:Diphenhydramine / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000502:physiology; D006632:Histamine / Q000494:pharmacology*; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D011968:Receptors, Histamine / Q000187:drug effects; D011969:Receptors, Histamine H1 / Q000187:drug effects / Q000502:physiology; D011970:Receptors, Histamine H2 / Q000187:drug effects / Q000502:physiology; D013552:Swine; D013890:Thiourea / Q000494:pharmacology
D011968:Receptors, Histamine; D011969:Receptors, Histamine H1; D011970:Receptors, Histamine H2; D002927:Cimetidine; D006632:Histamine; D004155:Diphenhydramine; D013890:Thiourea; D017259:Dimaprit