Pregnancy alters cortisol feedback inhibition of stimulated ACTH: studies in adrenalectomized ewes.
These studies test the hypothesis that pregnancy alters the feedback effects of cortisol on stimulated ACTH secretion. Ewes were sham-operated (Sham), or adrenalectomized (ADX) at approximately 108 days gestation and replaced with aldosterone (3 microg x kg(-1) x day(-1)) and with cortisol at either of two doses (ADX + 0.6 and ADX + 1 mg x kg(-1) x day(-1)); ewes were studied during pregnancy and postpartum. Mean cortisol levels produced in ADX ewes were similar to normal pregnant ewes (ADX+1) or nonpregnant ewes (ADX+0.6), respectively. Plasma ACTH concentrations in response to infusion of nitroprusside were significantly increased in the pregnant ADX+0.6 ewes (1,159 +/- 258 pg/ml) relative to pregnant Sham ewes (461 +/- 117 pg/ml) or the ADX+1 ewes (442 +/- 215 pg/ml) or the same ewes postpartum (151 +/- 69 pg/ml). Plasma ACTH concentrations were not significantly different among the groups postpartum. Increasing plasma cortisol to 20-30 ng/ml for 24 h before hypotension produced similar inhibition of ACTH in all groups. Pregnancy appears to decrease the effectiveness of low concentrations of cortisol to inhibit ACTH responses to hypotension.
Keller-Wood
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Department of Pharmacodynamics, University of Florida, Gainesville, Florida 32610, USA. kellerwd@cop.ufl.edu
Wood
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D000315:Adrenalectomy; D000324:Adrenocorticotropic Hormone / Q000037:antagonists & inhibitors* / Q000097:blood; D000450:Aldosterone / Q000494:pharmacology; D000818:Animals; D000959:Antihypertensive Agents / Q000494:pharmacology; D001127:Arginine Vasopressin / Q000097:blood; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D001798:Blood Proteins / Q000032:analysis; D004305:Dose-Response Relationship, Drug; D004573:Electrolytes / Q000097:blood; D005246:Feedback; D005260:Female; D006854:Hydrocortisone / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology / Q000502:physiology*; D007022:Hypotension / Q000097:blood / Q000139:chemically induced / Q000503:physiopathology; D009599:Nitroprusside / Q000494:pharmacology; D049590:Postpartum Period / Q000502:physiology; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000502:physiology*; D012016:Reference Values; D012756:Sheep
D000959:Antihypertensive Agents; D001798:Blood Proteins; D004573:Electrolytes; D001127:Arginine Vasopressin; D009599:Nitroprusside; D000450:Aldosterone; D000324:Adrenocorticotropic Hormone; D006854:Hydrocortisone