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

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Abstract
Luteal and interstial cell RNA contents and circulating progesterone (P) and 20α‐hydroxypregn‐4‐ene‐3‐one (20α‐OH P) levels were measured during pseudopregnancy in order to characterize relationships between ovarian 20α‐OH P secretion and luteal regression. Functional luteolysis, as manifested in depressed P levels, was not associated with concurrent elevations in 20α‐OH P. Rather, augmented 20α‐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 20α‐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.