APStracts 2:0247R, 1995.

Effects of vasopressin v1 receptor blockade during acute and sustained hypovolemic hypotension. Wall, Barry M., Kim M. Huch, Keith R. Runyan, Hugh H. Williams, Haralambos Gavras, C. Robert Cooke. veterans affairs medical center, AND DEPARTMENT OF MEDICINE, UNIVERSITY OF TENNESSEE, MEMPHIS, TENNESSEE, AND DEPARTMENT OF MEDICINE, BOSTON UNIVERSITY, BOSTON MA

APStracts 2:0247R, 1995.

The response of vasopressin and its role in the maintenance of arterial pressure during and following the development of hypotensive central hypovolemia were studied in tilt table studies in quadriplegic subjects. The studies were performed during acute head -up tilting to a maximally tolerated degree of tilt (8 subjects) and during sustained head-up tilt following a 20% reduction in mean arterial pressure (MAP) (11 subjects). Studies in all subjects were performed on two separate days, once with and once without administration of a selective vasopressin V1 receptor antagonist. During acute head-up tilting, plasma vasopressin concentrations (Pavp) did not increase significantly until MAP decreased to 60 mmHg at maximal tilt. There was no difference in the degree of hypotension produced in the presence as compared to the absence of V1 receptor blockade. There was also no difference in plasma renin activity (PRA), or in plasma cortisol (Pc) or aldosterone (Pa) concentrations at maximal tilt. In contrast, during sustained head-up tilt following a 20% reduction in arterial pressures, systolic and mean arterial pressures were significantly lower and PRA was significantly higher in the presence than in the absence of V1 receptor blockade. Pavp increased, and was significantly higher after 30 minutes of sustained tilt than pre-tilt Pavp in supine posture. These studies do not provide evidence of a role for vasopressin in the maintenance of arterial pressure during the acute development of hypotensive hypovolemia in human subjects, but do provide evidence of a modest role for vasopressin in the maintenance of arterial pressure when the effect of hypovolemia is more moderate and sustained.

Received 17 January 1995; accepted in final form 24 August 1995.
APS Manuscript Number R33-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 23 September 1995.