ARE OVINE LEYDIG-CELLS ABLE TO AROMATIZE ANDROGENS

The conversion of testosterone into oestradiol by ovine Leydig cells c ultured in vitro was studied using the non-steroidal aromatase inhibit or CGS 16949A. Additionally, aromatase activity was detected by immuno histochemical staining of cultured Leydig cells or cryosections. The c ells were obtained from testes of Polish Mountain rams 5-6 months old (immature) or 12-15 months old (mature). Leydig cells were cultured al one (controls) or incubated for 6 h in the presence of testosterone. A romatase inhibitor was then added to the cultures which were incubated for a further 18 h. After a 24-h incubation period, testosterone and oestradiol secretion were determined by testing the culture medium usi ng radioimmunological methods. The addition of testosterone to the cul ture medium enhanced oestradiol synthesis, suggesting that exogenous t estosterone could also be aromatized to oestradiol by ovine Leydig cel ls in vitro. In the presence of CGS 16949A, the conversion of testoste rone to oestradiol was significantly suppressed in a dose-dependent ma nner. All Leydig cells obtained from testes of mature rams and stained immunohistochemically were positive for aromatase, whereas Leydig cel ls from immature males were negative. The localization of immunoreacti ve aromatase appeared to be dependent on the age of the donor ram. It is suggested therefore, that mature Leydig cells in the ram are not on ly the site for testosterone synthesis, they are also capable of conve rting androgens into oestrogens.