Nitric oxide synthase and tyrosine nitration in idiopathic asthenozoospermia: an immunohistochemical study.

To characterize the expression pattern of constitutive and inducible nitric oxide synthase (NOS) in spermatozoa isolated from normospermic fertile donors and asthenozoospermic infertile patients, by means of immunohistochemistry. Also to evaluate the immunohistochemical expression of citrulline, a marker of NOS activity, and nitrotyrosine, which indicates the formation of peroxynitrite, which may affect sperm functionality through its cytotoxic action. Prospective study. Academic male infertility center. Twenty-nine infertile patients affected by idiopathic asthenozoospermia and 26 age-matched normospermic fertile donors. Sperm parameters were evaluated, and immunohistochemical analysis was performed in isolated spermatozoa. Semen analyses, to ascertain volume, sperm count, motility, and morphology. Immunohistochemical expression of NOS isoforms, citrulline, and nitrotyrosine. Constitutive NOS expression was greater in spermatozoa isolated from normospermic fertile donors. In contrast, the immunohistochemical expression of inducible NOS and nitrotyrosine was higher in asthenozoospermic samples. Our data concerning citrulline indicated enhanced NOS activity in sperm from idiopathic asthenozoospermic patients. Our results support the hypothesis that increased NOS activity and an excess of tyrosine nitration may affect the functional characteristics of spermatozoa in idiopathic asthenozoospermia.