Biology of Reproduction, Vol 12, 599-608, Copyright © 1975 by Society for the Study of Reproduction

Metabolism of Progesterone by Rat Ovarian Tissue: Influence of Pregnant Mare Serum Gonadotropin and Prolactin

¹ Department of Obstetrics and Gynaecology and Department of Physiology, University of Western Ontario, London, Ontario, Canada

Homogenates of non-luteal tissue (interstitial cells plus follicles) from immature rat ovaries have been incubated in phosphate buffer, pH 6.9 containing 10^-3 M NADPH and 10^-4 M progesterone-4-¹⁴C. Thirteen radioactive metabolites have been isolated, nine of which have been identified by recrystallization to constant specific radioactivity following addition of carrier steroids. The others have been identified provisionally, on the basis of chromatographic mobility in several thin layer chromatography systems, both as free compounds and as acetate derivatives. The effect, upon progesterone metabolism, of pre-treatment with 4 IU pregnant mare serum gonadotropin (PMS) to induce a single crop of corpora lutea, and of prolactin treatment (100 µg NIH-P-B2 twice daily) beginning 5 days before autopsy was investigated in a 2 x 2 factorial design experiment. Pre-treatment with PMS significantly decreased the rates of formation, by non-luteal tissue, of metabolites identified as androstenedione, 3-hydroxy-5-pregnan-20-one, 3-hydroxy-5-androstan-17-one, and provisionally as androsterone, 3, 17-dihydroxy-5-pregnan-20-one. 3, 17-dihydroxy-5-pregnan-20-one, and testosterone. The same treatment was associated with significantly increased production of compounds identified as 5-pregnan-3,20-dione, 20-hydroxypregn-4-en-3-one, and provisionally as 5-pregnan-3,20-diol. Prolactin caused significant decreases in production of 20-hydroxypregn-4-en-3-one, 5-pregnan-3,20-diol and of 5-androstan-3, 17-diol and/or 5-androstan-3,l7-diol. In addition, prolactin resulted in statistically significant reduction in overall conversion of progesterone to all metabolic products examined. No statistically significant interactions of treatments were detected, for any metabolites. There was no evidence of formation of either estrone or estradiol-17 in any of the treatment groups.