Background: Cryptorchidism is caused following any failure in the descending scrotum at the birth and is one cause of the infertility in the human and some animal species. In most mammalian species, the temperature of testis is a few degrees lower than the abdominal cavity which is necessary for the maintenance of normal spermatogenesis. The aim of the present study was to investigate the process of apoptosis in testicular tissue of adult rat following unilateral experimental cryptorchidism.

Materials and Methods: Adult male Wistar rats (200-250 g) were divided into 15 groups, each containing 8 animals. Experimental unilateral cryptorchidism was carried out in 7 groups using the fixation of right testis to the abdominal wall. In seven groups the testes were assessed 1, 3, 6, 10, 15, 30 and 60 days postoperative. In another seven groups, as sham, the testis was displaced from scrotum to the abdominal cavity. Then the testis was returned to the scrotum. One group, as the control, bore with no procedure. Following the sampling of the testicular tissue and the later fixation the testes were studied for apoptosis.

Results: The tunnel staining identified that the experimental cryptorchidism induces apoptosis in germinal cells of testicular tissue. Peak of the apopetotic cell numbers were observed in third and sixth day postoperative. There was no significant difference between the sham and control groups.

Conclusion: Our results showed that the experimental cryptorchidism induced apoptosis in testicular tissue. The peak of cell death is three days postoperative then it gradually the decreases with elapsing time. This effect was probably the result of thermal and oxidative stress in testicular cells.