Vasomotor effect of histamine on pig and cattle coronary artery in vitro.

Abstract

ABSTRACT-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 Hi-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. Remarkable species differences have been reported concerning the responsiveness of coronary vessels to histamine in vitro. Coronary arteries from monkeys and dogs respond to histamine with relaxations (1, 2), while human, pig and cattle coronary arteries respond with contractions (3-6).It has been postulated that the species difference might depend on the ability of histamine to activate H1-and H2-receptors in vascular smooth muscle and H1-receptors in endothelium, which possibly mediate the release of prostaglandin 12 (7, 8) or endothelium-derived relaxing factors (1,9,10

Vasomotor effects of histamine on bovine and equine basilar arteriesin vitro

“…Its pA 2 value for bovine basilar arteries (7.61 _+ 0.11) was similar to that demonstrated with porcine basilar (7.77 -+ 0.06; Miyamoto and Nishio, 1993) and coronary arteries (7.80 -+ 0.07;Obi et al, 1991a). Its pA 2 value for equine basilar arteries (8.15 -+ 0.07) was virtually identical to that determined previously (8.14 -+ 0.06; Obi et al, 1991b).…”