RESUMEN
<p><b>OBJECTIVE</b>To investigate the relationship between germ cell apoptosis and expressions of Bcl-2 and Bax in contralateral testes of experimental unilateral cryptorchid rats.</p><p><b>METHODS</b>Twenty male Sprague-Dawley rats were randomly divided into 2 groups (namely cryptorchid group and control group), with 10 rats in each group. Cryptorchid animal model was established, and contralateral testes were captured 90 days later. The evidence of germ cell apoptosis was detected by TUNEL assay. The expressions of Bcl-2 and Bax were detected by immunohistochemical method.</p><p><b>RESULTS</b>In the contralateral testes of experimental unilateral cryptorchidism, apoptosis index of germ cell and Bax expression significantly increased compared with those in the control group, respectively (P < 0.01), while Bcl-2 expression and testis weight obviously decreased (P <0.01). The apoptotic cells were mostly pachytene spermatocytes and round spermatids.</p><p><b>CONCLUSION</b>The germ cell apoptosis is highly correlated with expressions of Bcl-2 and Bax in contralateral testes of experimental unilateral cryptorchidism. Bcl-2/Bax plays an important role in germ cell apoptosis.</p>