The ontogeny and regulation of corticosteroid secretion by the ovine foetal adrenal.

Adrenal glands of foetal sheep of 40 days gestation to term were incubated with and without ACTH or an increased [K-+]. With ACTH, the 40 day foetal adrenal was capable of producing more cortisol and aldosterone per g body weight than was the term adrenal. ACTH was a potent stimulus to aldosterone and cortisol production in foetuses aged 60-90 days, and this effect declined significantly in the 91-120 day period. An increased [K-+] was stimulatory to aldosterone production only after 120 days gestation. Peripheral blood levels of aldosterone, corticosterone, cortisol, 11-deoxycortisol and 11-deoxycorticosterone were measured in foetuses 60 days to term and the levels of aldosterone and cortisol were significantly lower in 90-120 day foetuses than in the younger or older ones. Direct adrenal vein cannulation proved all five steroids to be secretory products of the foetal adrenal.