RESUMEN
<p><b>OBJECTIVES</b>To investigate the effect of senility on inducible nitric oxide synthase (iNOS) expression and apoptosis in rat penis.</p><p><b>METHODS</b>The rats were divided into three groups randomly: senescent, aged and young. Their penises were harvested to detect iNOS expression by immunohistochemistry and cell apoptosis rate by TUNEL, respectively.</p><p><b>RESULTS</b>iNOS expression were 0.24 +/- 0.03, 0.17 +/- 0.02, 0.12 +/- 0.03 (relative A) and cell apoptosis rate were (1.41 +/- 0.78)%, (0.94 +/- 0.43)% and (0.50 +/- 0.23 )%, respectively, in the tissues of three groups. The differences among three groups were considerable significance (P <0.05).</p><p><b>CONCLUSION</b>It maybe one of the mechanisms of erectile dysfunction in the aging male that senility causes the increase of iNOS expression and cell apoptosis.</p>