Influence of municipal effluents on the expression of connexins in the brook trout ( Salvelinus fontinalis) testis

Abstract

Gap junctions are essential for spermatogenesis. Exposure to municipal wastewater effluent can modify spermatogenesis in fish. The present aim was to determine if municipal wastewater effluent could alter the expression of testicular connexins (Cxs) in brook trout. Trout were exposed for 4 and 12 weeks to various concentrations of municipal effluent (0, 1, 10 and 20%, v/v). Hepatic vitellogenin ( vtg) mRNA levels were not different between exposure groups after 4 weeks. At this time, testicular cx43 and cx31 mRNA levels increased in the 1% group, but cx30 and cx43.4 levels were not different at any concentration. Immunolocalization of each Cx did not differ between groups after 4 weeks. After 12 weeks, spermatogenesis in the 1% group was more advanced than in other groups, and hepatic vtg mRNA levels were significantly increased at the higher exposure concentrations. Testicular cx43 mRNA levels were higher than controls at all doses, while cx43.4 levels increased in a dose-dependent manner but remained lower than controls. cx31 mRNA levels were significantly lower in the 1 and 10% groups than in control and 20% group, while cx30 levels did not vary. Immunolocalization of Cxs did not differ between groups except for Cx43.4, which was expressed between spermatocytes in the 1% group. Furthermore, the Cx31 immunoreaction appeared to decrease in testicular blood vessels of fish exposed to the highest dose. Furthermore, vegf mRNA levels were unaltered by treatment at both time points. Thus, long-term exposure to environmental concentrations of wastewater effluent can alter the expression of testicular Cxs.