Germ cell apoptosis and endothelial nitric oxide synthase (eNOS) expression following ischemia-reperfusion injury to testis

There is evidence to suggest that reactive oxygen species (ROS) are involved in ischemia-reperfusion injury to the testis. Nitric oxide (NO), a ubiquitous free radical produced by the nitric oxide synthases (NOS), has been implicated in physiologic and pathologic interactions with ROS. We examined the effect of testicular ischemia on germ cell apoptosis and endothelial NOS (eNOS) expression. Adult rats were subjected to unilateral 720 degrees testicular torsion for 1 or 3 hours and 24 hours later, testes were harvested for immunohistochemical studies. Apoptosis was detected by in situ 3' end-labeling of DNA with digoxigenin-ddUTP and eNOS protein was detected using an eNOS monoclonal antibody. Testes subjected to 3 hours of torsion had a threefold increase in apoptotic germ cells per cross-sectional area compared to sham testes (P <.05). In addition to its known expression in Leydig, Sertoli, and vascular endothelial cells, eNOS was detected in the cytoplasm of degenerating germ cells. Consecutive testis sections stained for eNOS and cellular DNA fragmentation demonstrated co-localization of eNOS protein and germ cell apoptosis. The detection of strong immunostaining in apoptotic germ cells supports a role of eNOS in germ cell degeneration after testicular ischemia-reperfusion and suggests that NO is associated with germ cell apoptosis.