Cardiovascular actions of kinins in the rabbit

Abstract

The results obtained in this study indicate that the complex cardiovascular effect of BK in vivo may result from direct actions on vascular smooth muscles, presumably mediated by at least two types of receptors, as well as from the release of endogenous prostaglandins. BK and congeners exert a direct action on vascular smooth muscle by stimulating specific receptors both of the B1 type (in the aorta, the large arteries, and the mesenteric vein) and of the B2 type (in the jugular vein); and these vascular tissues provide useful preparations for pharmacological studies of bradykinins. Isolated organs perfused through their main arteries with physiological medium respond to BK by an increase of perfusion pressure (vasoconstriction in isolated ears and kidneys) or by a decrease (vasodilation in the rabbit heart). The vascular effects of BK in the heart and the kidney depend in part on the release of endogenous prostaglandins and on the activation of receptors that appear to be of the B2 type.Like other endogenous hypotensive agents, BK appears to reduce the tonus of the peripheral vessels, while contracting large arteries and veins. The results obtained in vitro are discussed with respect to the hypotensive effect in vivo and to the role of kinins in inflammation and oedema.