Inhibition of stimulated and basal acth by cortisol during ovine
pregnancy.
Keller-Wood, Maureen.
Departments of Pharmacodynamics and Physiology, University of
Florida, Gainesville, FL 32610
APStracts 3:0021R, 1996.
In pregnant ewes, as in pregnant women, plasma ACTH and cortisol
concentrations are increased. Inhibition of free cortisol
concentrations by dexamethasone, a synthetic glucocorticoid, is
reduced in pregnant women as compared to nonpregnant women. These
experiments were designed to test the hypothesis that basal and
stimulated ACTH concentrations are less sensitive to negative
feedback inhibition by cortisol in pregnant ewes than in nonpregnant
ewes. Ewes were infused with vehicle and with cortisol at two
different rates (1 and 2 [mu]g/kg/min) for one hour; plasma ACTH
concentrations during and after the infusion and after subsequent
stimulation by hypotension were measured. Basal plasma ACTH
concentrations during a two hour infusion of cortisol (2
[mu]g/kg/min) were also measured in undisturbed ewes. Cortisol
significantly inhibited both stimulated and basal ACTH. The degree of
suppression of ACTH was not reduced in the pregnant ewes as compared
to the nonpregnant ewes. The results indicate that both basal and
stimulated ACTH are sensitive to negative feedback inhibition by
cortisol during ovine pregnancy.
Received 13 September 1995; accepted in final form 15 January
1996.
APS Manuscript Number R570-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 25 January 96