Maturational changes in steroidogenic enzyme activities metabolizing testosterone and dihydrotestosterone in two populations of testicular interstitial cells.

The present study examined changes in steroidogenic enzyme activities which metabolize testosterone or dihydrotestosterone between days 21-73 of maturation in Band 2 and Band 3 cells isolated by centrifugation of rat testicular interstitial cells on metrizamide density gradients. 5 alpha-reductase and 17 beta-hydroxysteroid dehydrogenase activities increased progressively in Band 2 and Band 3 cells between days 21-35 of maturation, then both enzyme activities declined to reach low levels in adult Band 2 and Band 3 cells. The significantly higher activities of both enzymes in Band 3, which contains a greater concentration of Leydig cells at each age, suggest their localization in Leydig cells. 5 alpha-androstane-3 alpha- and 3 beta-hydroxysteroid dehydrogenase activities increased in both Band 2 and Band 3 cells between days 21-50 of maturation and remained elevated; however, dihydrotestosterone was metabolized primarily to 5 alpha-androstane-3 beta,17 beta-diol in Band 2 cells, while 5 alpha-androstane-3 beta,17 beta-diol was the major metabolite of dihydrotestosterone in Band 3 cells. These studies suggest that testosterone accumulation during sexual maturation can be influenced by changing patterns of 5 alpha-reductase and 17 beta-hydroxysteroid dehydrogenase activities which metabolize testosterone, and of 5 alpha-androstane-3 alpha- and 3 beta-hydroxysteroid dehydrogenase activities which metabolize dihydrotestosterone in both Band 2 and Band 3 cells.