Quantitative cytochemical analyses of ovarian luteal and interstitial cell RNA in relation to plasma progestins during pseudopregnancy in the rat.

Luteal and interstitial cell RNA contents and circulating progesterone (P) and 20 alpha-hydroxypregn-4-ene-3-one (20 alpha-OH P) levels were measured during pseudopregnancy in order to characterize relationships between ovarian 20 alpha-OH P secretion and luteal regression. Functional luteolysis, as manifested in depressed P levels, was not associated with concurrent elevations in 20 alpha-OH P. Rather, augmented 20 alpha-OH P levels were evidenced in periovulatory periods at the onset and termination of pseudopregnancy, subsequent to RNA accumulation in both luteal and interstitial compartments. It is postulated that 20 alpha-OH P, the putative inactive metabolite of P, is produced by both ovarian compartments in a cyclic manner and in response to gonadotrophin released in the preovulatory period.