ARGININE-VASOPRESSIN AND OXYTOCIN RESPONSES TO ANGIOTENSIN-II ARE MEDIATED BY AT1 RECEPTOR SUBTYPE IN NORMAL MEN

This study was performed to determine whether the stimulatory effect o f plasma angiotensin II (ANG II) on arginine vasopressin (AVP) and oxy tocin (OT) secretion in humans is mediated by AT1 subtype receptors. F or this purpose, the effects of the AT1 receptor antagonist losartan ( 50 mg orally) or a placebo on the AVP and OT responses to ANG II (intr avenous infusion for 60 minutes of successively increasing doses of 4, 8, and 16 ng/kg min; each dose for 20 minutes) administration were ev aluated in seven normal men. In additional experiments, the same subje cts were tested with losartan (50 mg orally) alone or placebo alone. N either losartan nor placebo given alone modified the basal levels of A VP and Oi. ANG II infusion induced significant increments in both seru m AVP and OT levels (mean peaks were 1.55 and 1.41 times higher than b aseline, respectively). Both hormonal responses to ANG II were complet ely abolished by pretreatment with losartan. These data provide eviden ce of Ail receptor involvement in mediation of the ANG Ii-stimulating effect on AVP and OT secretion. Copyright (C) 1998 by W.B. Saunders Co mpany.