Expression of nitric oxide synthase isoforms in the testes of pigs.

This study examined the expression of three isoforms of nitric oxide synthase (NOS) in the testes of pigs. Immunohistochemical studies demonstrated the presence of nNOS, eNOS and iNOS in interstitial cells, primary spermatocytes and spermatids. Positive immunoreactions for eNOS and iNOS were detected in peritubular myoid cells. Some vascular endothelial cells were positive for nNOS and eNOS. The expression of nitrotyrosine was detected in interstitial cells. In addition, the histochemical study revealed that all the interstitial cells were stained positively for NADPH-diaphorase, although some spermatids and vascular endothelial cells displayed moderate enzymatic activity. These findings suggest that three isoforms of NOS are expressed in the testis of pig and that they play important roles in the biology of interstitial cells that produce testosterone, as well as in spermatogenesis in the seminiferous tubules.