The activity of the enzymes involved in the antioxidant defence -superoxide dismutase (SOD), glutathione peroxidase (GPx), reductdse (GR), S-transferase (GST) ~ as well as the glutathione (GSH) levels were measured in different rat testicular cell populations. A differential distribution of these components among testicular cell types was clearly observed. Sertoli and peritubular cells had elevated SOD and GSH-dependent enzyme activities associated with a high GSH content. Compared with the somatic cells, pachytene spermatocytes (PS) and round spermatids (RS) presented a different antioxidant system characterized by higher SOD activity and GSH content associated with very low GSH-dependent enzyme activity. Spermatozoa exhibited the same enzymatic system as PS and RS but were devoid of GSH. Interstitial tissue displayed high GSH content, moderate SOD and GSH-related enzyme activity except for GPx which was very elevated. It is concluded that the different categories of testicular cells probably display a highly variable susceptibility to oxidative stress.

To elucidate the mechanisms through which 2-mercaptoacetate administration inhibits fatty acid oxidation in the liver, the respiration rates induced by different substrates were studied polarographically in rat hepatic mitochondria isolated 3 h after 2-mercaptoacetate administration. Palmitoyl-L-carnitine oxidation was almost completely inhibited in either the absence or presence of malonate. Octanoate oxidation was also inhibited, and the intramitochondrial acyl-CoA content was markedly increased. The oxidation rate of pyruvate and 2-oxoglutarate on the one hand and of 3-hydroxybutyrate, succinate and glutamate on the other was either normal or only slightly decreased. In the presence of 2,4-dinitrophenol, the extent of the inhibition of palmitoyl-L-carnitine oxidation was unchanged. All these results are consistent with the hypothesis that the 2-mercaptoacetate inhibition of fatty acid oxidation is due to an inhibition of the beta-oxidation pathway itself. Finally, the mitochondrial defect responsible for this inhibition was shown to be an inhibition of palmitoyl-CoA dehydrogenase activity (EC 1.3.99.3).

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-1alpha 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.