ABSENCE OF 5-DELTA-REDUCTASE ACTIVITY IN THE GUBERNACULUM DURING DESCENT OF THE FETAL PIG TESTIS

To evaluate the hypothesis that testicular descent is mediated by the action of high local concentrations of dihydrotestosterone in the gube rnaculum, testis, or epididymis, we obtained tissues from 30 male pig fetuses between 63 and 101 days of gestation. We assayed the 5alpha-re ductase activity in homogenates of pooled tissue by following the conv ersion of (H-3)testosterone to (H-3)dihydrotestosterone. The 5alpha-re ductase activity in the urethra and prostate increased prior to and du ring, but decreased after, the period of testicular descent. The 5alph a-reductase activity in the gubernaculum remained constant throughout gestation and was not significantly higher than the background activit y found in umbilical cord, testis plus epididymis, striated thigh musc le and heat inactivated samples of prostate and urethra. Prior to test icular descent, the 5alpha-reductase activity was approximately 60 to 300 times higher in the urethra than in the gubernaculum, and approxim ately 20 to 55 times higher in the prostate than in the gubernaculum. These findings indicate that local conversion of testosterone to dihyd rotestosterone in the gubernaculum or epididymis does not play a role in the mediation of testicular descent in the pig fetus.