CONTRACTILE RESPONSES OF HUMAN DEFERENTIAL ARTERY AND VAS-DEFERENS TOVASOPRESSIN

We studied the effects of vasopressin on isolated rings of human defer ential artery and vas deferens (prostatic portion) obtained from patie nts undergoing radical cystectomy (n = 11) or prostatectomy (n = 10). Ring segments of artery or vas deferens were studied in organ bath exp eriments at optimal resting tension. In artery rings, vasopressin prod uced concentration-dependent, endothelium-independent contractions wit h an EC(50) of 4.5 X 10(-10) M. The presence of N-G-nitro-L-aginine me thyl eater hydrochloride (10(-4) M), an inhibitor of nitric oxide synt hase, did not change significantly (P > 0.05) the vasopressin-induced contraction. In ring preparations of the prostatic part of the vas def erens, vasopressin induced phasic contractions with an EC(50) of 7.0 x 10(-9) M. The vasopressin V-1 receptor antagonist, d(CH2)(5)Tyr(Me)AV P (10(-8) and 10(-6)), displaced to the right in parallel the control curve to vasopressin in artery and vas deferens rings. These results i ndicate that vasopressin exerts a powerful constrictor action on human deferential artery and vas deferens by direct stimulation of V-1 rece ptors. It is concluded that the deferential artery may dampen the pass age of blood to the vas deferens in circumstances characterized by inc reased plasma vasopressin levels.