Aromatase-inhibitors of the androstenedione-type activate the 17 beta-hydroxysteroid-dehydrogenase in the rat testis tissue suspension model.

In an in vitro rat testis cell suspension model, the metabolism of tritiated testosterone, dihydrotestosterone and androstenedione was investigated. In the presence of aromatase inhibitors like 1-methyl-androsta-1,4-dien-3,17-dione (SH 489) and 4-hydroxy-androstenedione, the metabolism was shifted towards 17-keto forms. The same effect was observed in the presence of androstenedione, the parent compound of the two aromatase inhibitors. The consequent consideration of the whole labelled steroidal spectrum in each experiment leads to the conclusion that androstenedione and the derived aromatase inhibitors activate the 17 beta-hydroxysteroid-dehydrogenase in a product activating manner. Our results imply that aromatase inhibitors may regulate the intratissular levels not only of estrogens but also of other hormonally active steroids like dihydrotestosterone and 5-androstenedione.