Pituitary-adrenal function in the immature ovine foetus.
Pituitary-adrenal responses to intravenous infusion of ovine corticotrophin-releasing hormone (oCRH) or arginine vasopressin (AVP) and to haemorrhage were examined in the ovine foetus prior to 90 days of gestation (term 145-150 days). In chronically cannulated foetuses (n = 8), between 74 and 84 days of gestation, basal ACTH levels were less than 20 pg/ml while cortisol levels were 6.5 +/- 1.5 nmol/l (mean +/- S.E.M.). Intravenous infusion of oCRH (1 microgram/h for 60 min) or AVP (1 microgram/h for 60 min) significantly increased ACTH (P < 0.05 for both treatments) and cortisol (P < 0.01 for both treatments) levels, although the response to both hormones was modest. In acutely studied foetuses of a similar age (70-90 days of gestation, mean 82.0 +/- 1.4 days, n = 7), exteriorization and progressive haemorrhage significantly (P < 0.05) elevated ACTH levels from 117.4 +/- 32.1 pg/ml to a maximal value of 329.2 +/- 112.8 pg/ml, the maximal ACTH response corresponding to the removal of a volume of blood equivalent to 6.6 +/- 1.2% of the pre-haemorrhage body weight. The present study has demonstrated that the ovine foetal pituitary, in vivo, is responsive to exogenous and endogenous stimuli by mid-gestation and, at this age, although basal cortisol levels are low, the foetal adrenal is capable of responding to elevated ACTH levels in the short term.
McFarlane
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AC
Howard Florey Institute of Experimental Physiology and Medicine, University of Melbourne, Parkville, Victoria, Australia.
Potocnik
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S
Towstoless
M
M
Moritz
K
K
Wintour
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EM
D000324:Adrenocorticotropic Hormone / Q000097:blood / Q000378:metabolism*; D000818:Animals; D001127:Arginine Vasopressin / Q000494:pharmacology; D001815:Bloodletting; D003346:Corticotropin-Releasing Hormone / Q000494:pharmacology; D005865:Gestational Age; D006854:Hydrocortisone / Q000097:blood; D010913:Pituitary-Adrenal System / Q000196:embryology*; D012756:Sheep / Q000097:blood / Q000196:embryology*; D013312:Stress, Physiological / Q000097:blood
D001127:Arginine Vasopressin; D000324:Adrenocorticotropic Hormone; D003346:Corticotropin-Releasing Hormone; D006854:Hydrocortisone