Effects of HCG and PMS on bioconversion of progesterone, androstenedione and testosterone in immature rat testes

The present study was conducted to determine whether exogenous gonadotropins will alter the 5α-reductase activity in immature rat testes. Newborn and 10-day-old rats were treated with either human chorionic gonadotropin (HCG, 50 IU/day) or pregnant mare serum (PMS, 50 IU/day). All the animals were sacrificed at 20 days of age. Testicular tissue was incubated with three different radiolabeled substrates: [ 3H]-progesterone, [ 3H]-androstenedione or [ 3H]-testosterone. The percentage of conversion of progesterone or androstenedione to testosterone was essentially unchanged; formation of 5α-reduced androgens was not prevented but greatly reduced. When testosterone was used as substrate, it was avidly metabolized by testicular tissue of 20-day-old rats of both groups, those treated with gonadotropins and the untreated controls. The data show that daily administration of gonadotropins to male rats, started either at day 1 or at day 10 from birth, significantly alter the steroid metabolism in the testes of 20-day-old rats. Specifically, the activities of 5α-reductase and 3α-hydroxysteroid dehydrogenase are drastically changed.