3β-HYDROXYSTEROID DEHYDROGENASE IN THE FOETAL MOUSE LEYDIG CELL

SUMMARY Five male foetal mice were killed daily from the 11th day of gestation until term, the 21st day. Sections of testis from every animal were incubated with three steroid substrates to demonstrate 3β-hydroxysteroid dehydrogenase histochemically. The substrates were (1) 3β-hydroxypregn-5-en-20-one (pregnenolone), (2) 3β,17α-dihydroxypregn-5-en-20-one (17α-hydroxypregnenolone), and (3) 3β-hydroxyandrost-5-en-17-one (DHA). With pregnenolone as substrate 3β-hydroxysteroid dehydrogenase activity was demonstrable from the 11th day, when the testis is first histologically recognizable, until the end of gestation. Using 17α-hydroxypregnenolone, no 3β-hydroxysteroid dehydrogenase activity was present in the foetal testis. With DHA as substrate weak activity was first seen in the testis of the 15-day foetal mouse, and increased steadily thereafter. These findings are thought to support the concept of substrate-specific 3β-hydroxysteroid dehydrogenases.