3-BETA-HYDROXYSTEROID DEHYDROGENASE-ACTIVITY AND GESTAGEN CONCENTRATIONS IN BOVINE COTYLEDONS AND CARUNCLES DURING GESTATION AND PARTURITION

3 beta-Hydroxysteroid dehydrogenase (3 beta-HSD) activity in bovine co tyledons was much higher than in caruncles throughout the gestation pe riod. The activity of this enzyme in cotyledons increased greatly to 1 50.6 +/- 5.8 pmol min(-1) mg(-1) protein during the seventh mg month o f gestation, reached a peak of 221.0 +/- 34.9 pmol min(-1) mg(-1) prot ein during the mg eighth month, and decreased at parturition. Progeste rone and 20 alpha-hydroxyprogesterone concentrations in cotyledons als o increased sharply to 2.69 +/- 0.30 and 2.15 +/- 0.42 ng mg(-1) prote in, respectively, during the seventh month of gestation, reaching peak s of 2.86 +/- 0.47 and 2.51 +/- 0.36 ng mg(-1) protein, respectively, during the eighth month and decreasing at parturition, in a manner sim ilar to the activity of 3 beta-hydroxysteroid dehydrogenase. The fluct uation of 17 alpha-hydroxyprogesterone concentration in cotyledons was different from that of progesterone and 20 alpha-hydroxyprogesterone. These findings indicate that the activity of 3 beta-hydroxysteroid de hydrogenase in the placenta is enhanced during the third trimester, an d progesterone synthesized in the cotyledons is converted concurrently to 20 alpha-hydroxyprogesterone before progesterone is transferred to the fetal blood.