Abstract:
The conversion of testosterone into oestradiol by ovine Leydig cellsculturedin vitro was studied using the non-steroidalaromatase inhibitor CGS 16949A. Additionally, aromatase activity was detectedby immunohistochemical staining of cultured Leydig cells or cryosections. Thecells were obtained from testes of Polish Mountain rams 5-6 months old(immature) or 12-15 months old (mature). Leydig cells were culturedalone (controls) or incubated for 6 h in the presence of testosterone.Aromatase inhibitor was then added to the cultures which were incubated for afurther 18 h. After a 24-h incubation period, testosterone and oestradiolsecretion were determined by testing the culture medium usingradioimmunological methods.The addition of testosterone to the culture medium enhanced oestradiolsynthesis, suggesting that exogenous testosterone could also be aromatized tooestradiol by ovine Leydig cells in vitro. In thepresence of CGS 16949A, the conversion of testosterone to oestradiol wassignificantly suppressed in a dose-dependent manner. All Leydig cells obtainedfrom testes of mature rams and stained immunohistochemically were positive foraromatase, whereas Leydig cells from immature males were negative. Thelocalization of immunoreactive aromatase appeared to be dependent on the ageof the donor ram. It is suggested therefore, that mature Leydig cells in theram are not only the site for testosterone synthesis, they are also capable ofconverting androgens into oestrogens.