Progesterone and its reductive metabolism in steroidogenic tissues of the developing hen embryo

Progesterone contents of adrenals and ovaries and the--mainly reductive--metabolism of [3H]progesterone by these organs and liver were investigated in hen embryos between Days 13 and 21 (hatching). Progesterone contents are similar in adrenals and ovaries on Day 13 (approx 3.5 ng/mg) but descend in characteristic manners toward Day 17 and rise steeply, only in the ovaries, then descend in these organs toward hatching. [3H]Progesterone is converted by the adrenals toward 12 main metabolites, the main glucocorticoid being corticosterone (B), and the main reduced metabolite, 5 beta-pregnane-3,20 dione (5 beta-P). On day 13, 5 beta-P is five times as important as B, but both steroids evolve in a symmetric fashion, so that at hatching this proportion is reversed. In all tissues at all stages, except the liver on Day 13, the yields of 5 alpha-pregnane-3,20 dione (5 alpha-P) are one order of magnitude below those of 5 beta-P. Both diones exhibit maxima on Day 17, probably extending until Day 19. Concomitantly, [3H]progesterone disappearance is maximal on Day 17. Both ovaries differ in the shape of their 5 alpha-P/5 beta-P curves in that the left ovary exhibits for this curve a function ascending continuously toward hatching.