5 alpha-reductase activity regulates testosterone accumulation in two bands of immature cultured Leydig cells isolated on Percoll density gradients.

The 5 alpha-reductase inhibitor, 4-methyl-4-aza-3-oxo-5 alpha-pregnan-20(s)-carboxylate was utilized to examine maturational changes in testosterone synthesizing capacity of Leydig cells localizing in Band 2 and Band 3 of Percoll density gradients. Immature Band 2 Leydig cells (from 25- to 39-day-old rats) cultured without the 5 alpha-reductase inhibitor, produced increased testosterone in response to hCG or 8-br-cAMP; however, basal, hCG- or 8-br-cAMP-stimulated testosterone accumulation was 4- to 12-fold higher when cells were cultured in the presence of inhibitor. Band 2 cells from older rats produced much less testosterone in response to hCG or 8-br-cAMP (less than 3.5 pmol/10(5], even when cultured with the inhibitor. Although immature Band 3 cells cultured in the absence of 5 alpha-reductase inhibitor produced increased testosterone in response to hCG or 8-br-cAMP, testosterone levels were relatively low, because elevated 5 alpha-reductase prevented appreciable androgen accumulation; however, Band 3 cells from older rats (over 39 days old) accumulated progressively more testosterone, because of the age-dependent decline in 5 alpha-reductase activity. Immature Band 3 cells cultured with the 5 alpha-reductase inhibitor accumulated 20- to 44-fold more testosterone in response to hCG of 8-br-cAMP.(ABSTRACT TRUNCATED AT 250 WORDS)