Steroid metabolism in the cortex and the medulla of the early fetal bovine ovary.

Suspensions of cells obtained from the cortex and the medulla of the ovary of early bovine fetuses of 4-10 cm in crown-rump (C-R) length were used for studies of the metabolism of radiolabeled exogenous steroid precursors. Tritiated dehydroepiandrosterone, androstenedione, and testosterone were employed as precursors and their metabolic products were evaluated after separation by thin-layer chromatography. The extent of conversion of tritiated dehydroepiandrosterone to androstenedione was higher in cells from medulla than in those from the cortex. Androstenedione was metabolized mainly to estrone, and the percent of transformation was similar in the cortex and the medulla, but the rate of formation of 17 beta-estradiol was higher in the medulla than in the cortex. Furthermore, cells obtained from the cortex and the medulla aromatized testosterone to 17 beta-estradiol at a similar rate. In all cases, the percent of transformation was higher in ovaries from fetuses of 4.0 cm in C-R length than those from fetuses of 9.0-10.0 cm in C-R length. These data suggest that, in the bovine fetal ovary, the activity of 3 beta-hydroxysteroid dehydrogenase/isomerase and 17 beta-hydroxysteroid dehydrogenase predominates in the medulla, whereas aromatase activity is similar in the cortex and the medulla of the early fetal bovine ovary.