SUMMARY
A broad expression of aromatase and estrogen receptors (ERs) in the testis suggests an important role for estrogens in regulating testicular cell function and reproductive events. The aim of the present study was to show whether Leydig cells in vitro isolated from cryptorchid testes of two inbred strains of mice, KE and CBA, are a site of estrogen synthesis. Using immunocytochemistry, aromatase, estrogen receptor · (ERa), and estrogen receptor b(ERb) were localized in cultured Leydig cells. Immunoreactive aromatase was found in the cytoplasm of control Leydig cells and those isolated from cryptorchid males, however the intensity of immunostaining was different, being stronger in Leydig cells deriving from cryptorchid mice. The strongest aromatase immunostaining was found in cryptorchid-KE Leydig cells. Strong immunoexpression of ERa was detected in the nuclei of both KE-and CBA-Leydig cells. The intensity of ERa immunostaining was stronger in cultured cells deriving from cryptorchid testes. ER‚ immunoexpression was detected predominantly in KELeydig cells. Control CBA-Leydig cells were negative for ER‚ or the result was inconclusive, whereas in cryptorchid CBALeydig cells a weak immunostaining was present in their nuclei. Western blot analysis confirmed the results obtained by immunocytochemistry. In KE- and CBA-Leydig cells aromatase as a band of 55 kDa protein was present, whereas ERa molecular weight was 67 kDa on Western blots. No band was detected for ERb. Radioimmunological analysis revealed that androgen and estrogen levels secreted by Leydig cells in vitro were strain-dependent. Additionally, in KE-Leydig cells that derived from cryptorchid mice estrogen level was distinctly higher in comparison with that of the respective control.