In vitro regulation of an inducible-type NO synthase in the rat seminiferous tubule cells

Rat Sertoli cells express an inducible nitric oxide synthase isoform (iNOS) in response to the combined addition of the cytokines-interferon gamma (IFNgamma), tumor necrosis factor (alpha) (TNF (alpha)), interleukin-(1alpha) (IL-(1alpha))-and lipopolysaccharides (LPS). We demonstrated that the addition of cytokines and lipopolysaccharides (C+L) to cultured peritubular cells resulted in high nitrite and iNOS mRNA levels, indicating the induction of an iNOS isoform. This enzyme was not induced in cultured pachytene spermatocytes or spermatids. Nitrite production in Sertoli cells and peritubular cells required both IFNgamma and TNF (alpha) and was potentiated by LPS, whereas IL-1(alpha) was ineffective. The induction of nitrite production and iNOS mRNA by IFNgamma+TNF (alpha)+LPS could be further enhanced by basic fibroblast growth factor in Sertoli cells but not in peritubular cells. In contrast, transforming growth factor (beta) markedly reduced this induction in peritubular cells but had no effect on Sertoli cells. FSH positively modulated the C+L-induced iNOS in Sertoli cells. Dibutyryl cAMP had a synergistic effect with C+L on NOS activity in both Sertoli cells and peritubular cells. In contrast, testosterone did not influence basal or induced NOS activity in these two cell types. These data show that NOS activity in the somatic cells of the seminiferous tubules is induced and regulated by multiple factors that act in combination, and suggest that nitric oxide may participate in the endocrine and paracrine control of testicular function.