Bcl-2 and Bax are involved in experimental cryptorchidism-induced testicular germ cell apoptosis in rhesus monkey

Apoptosis occurs spontaneously during spermatogenesis. However, little is known about its regulation in primate. Using an experimental cryptorchidism model in rhesus monkey, we have investigated the relationship between apoptosis and the Bcl-2 family members, Bcl-2 and Bax. Apoptotic cells were identified by in situ end labeling of fragmented DNA. The expressions of Bcl-2 and Bax in the testes during the heat stress-induced testicular germ cell apoptosis were detected by immunohistochemistry and Western blot techniques. The results showed that the apoptotic signals increased after heat treatment and the most susceptible cell types were spermatocytes and spermatids. A redistribution of Bax from the cytoplasmic to nuclear localization in some germ cells was observed. However, its total expression levels in the cells remained unchanged in the cryptorchid testes as determined by Western blot analysis; on the other hand, Bcl-2 levels increased significantly in response to heat stress. The subcellular redistribution of Bax and the increase in Bcl-2 expression in the cryptorchid testis suggest an involvement of Bcl-2 family members in heat stress-induced germ-cell apoptosis.