Activation of Mitogen Activated Protein Kinases and Apoptosis of Germ Cells After Vasectomy in The Rat

Abstract

Vasectomy induces a large amount of germ cell apoptosis. We examined the activation of mitogen activated protein kinases (MAPKs) in association with the apoptosis and proliferation of germ cells after vasectomy in the rat. Eight-week-old Wistar rats underwent bilateral vasectomy and the testes were harvested 1 to 9 days after vasectomy. Germ cell apoptosis was evaluated by terminal deoxynucleotidyl transferase mediated deoxyuridine triphosphate nick end labeling and electrophoretic assay of DNA fragmentation. Western blotting and immunohistochemistry were used to examine the temporal and spatial activation of signal regulated kinases 1/2, c-Jun-terminal kinases 1/2 and p38. Phospho-specific MAPK antibodies were used to examine their activations. Proliferation of germ cells was evaluated by proliferative nuclear cell antigen expression. Germ cell apoptosis was detected predominantly in primary spermatocytes with a peak 7 days after vasectomy. Signal regulated kinases 1/2, c-Jun-terminal kinases 1/2 and p38 were constitutively expressed in the control testis. Western blotting and immunohistochemistry showed rapid activation of signal regulated kinases 1/2, followed by activation of c-Jun-terminal kinases 1/2 and p38. Immunohistochemical study demonstrated the temporal and spatial relationships of apoptosis and MAPK activation in primary spermatocytes. On the other hand, proliferating cell nuclear antigen expression was enhanced in tetraploid spermatocyte and spermatogonia maximally 5 days after vasectomy. MAPKs were rapidly activated after vasectomy and germ cell apoptosis was observed after vasectomy. In contrast to the delayed phase up to 24 weeks after vasectomy, we observed hyperdynamic cellular turnover, spermatocyte loss through apoptosis and enhanced germ cell proliferation transiently at the early phase after vasectomy.