AJP - Regulatory, Integrative and Comparative Physiology, Vol 261, Issue 1 223-R230, Copyright © 1991 by American Physiological Society
Effect of ovariectomy on vasopressin, ACTH, and renin activity responses to hypotension
M. Keller-Wood and C. E. Wood
Department of Pharmacodynamics, University of Florida, Gainesville 32610.
The gonadal axis is thought to modulate adrenocorticotropic hormone (ACTH),
arginine vasopressin (AVP), and plasma renin activity (PRA) responses to
stimuli in several species. These experiments were designed to compare the
responses to hypotension in chronically ovariectomized ewes and intact
ewes. The ewes were infused with nitroprusside at rates of 5, 10, or 15
micrograms.kg-1.min-1 or infused with vehicle for 10 min. The response to
15 micrograms.kg-1.min-1 was also tested with or without treatment with 10
mg of dexamethasone 2 h before nitroprusside. Blood samples were collected
before and at 5, 10, 15, 20, and 30 min after the start of the infusion for
measurement of plasma ACTH, AVP, and PRA. In both groups of animals there
were significant responses to hypotension. There was a significant effect
of ovariectomy on ACTH, AVP, and PRA responses. ACTH and PRA responses were
lower in the ovariectomized ewes; AVP responses were increased in the
ovariectomized ewes. Administration of dexamethasone inhibited ACTH
responses and did not inhibit PRA responses in both groups of ewes.
Administration of dexamethasone did not inhibit the AVP response in the
intact ewes but did reduce the response in the ovariectomized ewes.
