Steroid metabolism by purified adult rat leydig cells in primary culture

Abstract

To characterize Leydig cell steroidogensis, we examined the metabolism of ( 3H)pregnenolone (3β-hydroxy-5-pregnen-20-one) to androgens in the presence and absence of human chorionic gonadotropin (hCG) as a function of culture duration. Approximately 20–30% of the ( 3H)pregnenolone was converted to testosterone (17 β-hydroxy-4-androsten-3-one) by purified Leydig cells at 0, 3 and 5 days (d) of culture. Androstenedione (4-androstene-3,17-dione) and dihydrotestosterone (17 β-hydroxy-5 α-androstan-3-one) were also produced while on day 5 of culture, significant amounts of progesterone (4-pregnene-3, 20-dione) were isolated. The Δ 5 intermediates, 17-hydroxypregnenolone (3β, 17-dihydroxy-5-pregnen-20-one) and dehydroepiandrosterone (3β-hydroxy-5-androsten-17-one), accounted for less than 1% of substrate conversion, indicating a clear preference for Leydig cells to metabolize ( 3H)pregnenolone via the Δ 4 pathway. On day 0 of culture, unidentified metabolites consisted of predominately polar steroids while on day 5 of culture, the unidentified metabolites consisted of predominately nonpolar steroids. In the presence of hCG, ( 3H)pregnenolone metabolism did not differ from basal on day 0 or 3 of culture. HCG increased the conversion of pregnenolone to progesterone and 17-hydroxyprogesterone (17-hydroxy-4-pregnene-3, 20-dione) on 5d. This suggests that Leydig cells cultured for 5d have decreased C 17–20 desmolase activity or that hCG acutely stimulates 3β-hydroxysteroid dehydrogenase and Δ 4-Δ 5 isomerase activities.