PHYSIOLOGICAL CONCENTRATIONS OF ARGININE-VASOPRESSIN ACTIVATE HUMAN PLATELETS IN-VITRO

Arginine vasopressin (AVP) is a neurohypophyseal peptide hormone with protean effects. Previous reports had shout that AVP stimulates platel ets, but only at concentrations 3-6 logs higher than the normal plasma concentrations in humans. In this study we tested the hypothesis that AVP, at physiologic concentrations, stimulated the expression of an a ctivation-dependent platelet antigen. Platelets obtained from normal v olunteers were incubated with increasing concentrations of AVP and the expression of the activation-dependent platelet antigen P-selectin (C D62) was determined by monoclonal antibodies and now cytometry. There was a concentration-dependent increase in CD62 expression with increas ing AVP concentration; at 1 PM AVP, 24.5% (1.3-88.5%) [median (range)] of platelets expressed CD62. The selective vasopressin V-1 receptor a ntagonist d(CH2)(5)-Tyr(me)AVP (TM-AVP) completely abolished AVP-stimu lated CD62 expression. We conclude that AVP can activate platelets at concentrations found in normal humans, at least in vitro, and that thi s response is mediated by the platelet V-1 receptor, AVP may be a phys iologic platelet agonist.