| Abstract: | Delta 5, 3 beta hydroxysteroid dehydrogenase activity was studied on mitochondrial and microsomal fractions of human and cat placentas. This activity was assessed by measuring the rate of 3H] progesterone formation from 3H] pregnenolone and of 3H] delta 4-androstenedione from 3H] dehydroepiandrosterone (DHA), by a double isotope dilution method. Specific activities measured under initial velocity conditions were similar in both human and cat placentas. However, the kinetics of the reaction with DHA as substrate exhibit a zoological specificity. |
