Conversion of progesterone by testicular tissue of cryptorchid rats.

The capacity of adult rat testes rendered surgically cryptorchid to metabolize progesterone was investigated at several time intervals (7, 14, 28 and 42 investigated at several time intervals (7, 14, 28 and 42 days) after surgery. Testicular tissue was incubated with [3H]progesterone, the steroid metabolites were isolated and purified using paper and thin layer chromatography, and further identified by isotopic dilution and recrystallization to constant 3H/14C ratio or constant specific activity (DPM/mumol). A sharp decrease in the accumulation of testosterone, concomitant with a marked increase in accumulation of 17 alpha-hydroxyprogesterone, was observed as early as 7 days after surgery. No further major changes were observed at 14 or 28 days after surgery. However, at 42 days, accumulation of testosterone was substantially increased, while that of 17 alpha-hydroxyprogesterone decreased to trace levels. 20 alpha-Dihydroprogesterone was detected at different time intervals after surgery. The data suggest that cryptorchidism inhibits the activity of 17-20 desmolase for the first 4 weeks after surgery. The activity of this enzyme is restored by the 42nd day and the metabolic pathway between progesterone and testosterone resembles that of an intact rat. The factors responsible for this spontaneous restoration of the biosynthetic pathway are under investigation.