Regulation of 3β-hydroxysteroid dehydrogenase activity by human chorionic gonadotropin, androgens, and anti-androgens in cultured testicular cells

Δ³-3β-Hydroxysteroid dehydrogenase is a key enzyme for testicular androgen biosynthesis and a marker for the Leydig cells. The hormonal regulation of this enzyme was studied in cultured rat testicular cells. Human chorionic gonadotropin (hCG) increased testosterone production in vitro while time course studies indicated a biphasic action of the gonadotropin on 3β-hydroxysteroid dehydrogenase activity. An initial stimulation (51%) of the enzyme was detected between 3 and 12 h of culture when medium testosterone was low. This is followed by an inhibition of 3β-hydroxysteroid dehydrogenase activity on days 2 and 3 of culture when medium testosterone was elevated. Concomitant treatment with a synthetic androgen (R1881) inhibited 3β-hydroxysteroid dehydrogenase activity and testosterone production in hCG-treated cultures while an anti-androgen (cyproterone acetate) increased 3β-hydroxysteroid dehydrogenase activity and testosterone biosynthesis. Addition of 10^-5 M spironolactone, an inhibitor of 17α-hydroxylase, blocked the hCG stimulation of testosterone production but increased medium progesterone. In the absence of the secreted androgen, hCG stimulated 3β-hydroxysteroid dehydrogenase activity in a time- and dose-related manner. Furthermore, hCG stimulation of 3β-hydroxysteroid dehydrogenase activity and progesterone accumulation in spironolactone-supplemented cultures was decreased by concomitant treatment with R1881 but was not affected by cyproterone acetate. The inhibitory effect of R1881 was blocked by the anti-androgen. In the absence of hCG, treatment with testosterone, dihydrotestosterone, or R1881, but not promegestone, alone also inhibited 3β-hydroxysteroid dehydrogenase activity while the inhibitory effect of testosterone was blocked by cyproterone acetate. Thus, hCG stimulates 3β-hydroxysteroid dehydrogenase activity in cultured testicular cells. The androgenic steroidogenic end products, in turn, inhibit this enzyme. The hormonal regulation of 3β-hydroxysteroid dehydrogenase activity may be important in the ultrashort loop autoregulation of androgen biosynthesis.