AJP - Regulatory, Integrative and Comparative Physiology, Vol 267, Issue 2 536-R541, Copyright © 1994 by American Physiological Society
Effects of gonadectomy on sexually dimorphic antidiuretic action of vasopressin in conscious rats
Y. X. Wang, J. T. Crofton, H. Liu, D. P. Brooks and L. Share
Department of Physiology and Biophysics, University of Tennessee, Memphis 38163.
The present study examined whether the antidiuretic response to vasopressin
is affected by the estrous cycle and by gonadectomy in conscious,
chronically instrumented hydrated rats. Infusion of vasopressin (10-100
pg.min-1.kg body wt-1) resulted in a dose-dependent antidiuresis. Urine
volume and free water clearance decreased and urinary osmolality increased
with no significant changes in mean arterial blood pressure, heart rate,
osmolar clearance, and urinary sodium and potassium excretion. The
antidiuretic response to vasopressin was significantly greater in intact
male and estrous female rats than in intact female rats in the other phases
of the estrous cycle. Thus the calculated doses of vasopressin to reduce
urine flow and free water clearance, as well as to increase urinary
osmolality 50% from their control values, were significantly higher in
nonestrous females than in males and estrous females. Gonadectomy was
without effect on the antidiuretic potency of vasopressin in males, but in
gonadectomized females the antidiuretic response to vasopressin was
enhanced to a level similar to that observed in intact males. These data
indicate that the antidiuretic activity of vasopressin is affected not only
by gender but also by phase of the estrous cycle and that the ovarian
hormone(s) may modulate the antidiuretic action of vasopressin.
