Receptors for kinins in isolated arterial vessels of dogs

A variety of kinin peptides, agonists and antagonists were tested with dog carotid and renal arteries in order to characterize kinin receptor types and functions. The dog carotid artery responds to bradykinin with concentration-dependent relaxation only when the endothelium is intact but des-Arg9-bradykinin is practically inactive. The effect of bradykinin is blocked by B2 receptor antagonists, suggesting that the dog carotid artery has B2 receptors in the endothelium. These receptors mediate relaxation of the arterial smooth muscles by promoting the release of an endothelium-derived relaxing factor whose action is prevented by methylene blue. Kinins relax the dog renal artery with or without endothelium. Methylene blue prevents the effect of bradykinin only, suggesting that B2 receptors, promoting the release of endothelium-derived relaxing factor, are present in the endothelium of the dog renal artery. Moreover, the dog renal artery appears to have both B2 and B1 receptors mediating relaxation of the arterial smooth muscle. The presence of the two receptor types has been demonstrated by means of specific agonists and antagonists. Indomethacin blocks the effects of both bradykinin and des-Arg9-bradykinin on the dog renal artery without endothelium, suggesting that muscular B1 and B2 receptors act by promoting the release of prostaglandins. Captopril, a kininase II inhibitor, potentiates the effect of bradykinin on the dog carotid artery more than on the dog renal artery.