Anti-estrogen prevents xenoestrogen-induced testicular pathology of eelpout (Zoarces viviparus)

In the present study, the effects of different concentrations of the estrogenic chemical 4-tert-octylphenol on vitellogenin (Vtg) synthesis and testicular structure were investigated in the eelpout Zoarces viviparus during spermatogenesis. Adult male eelpout were exposed to 4-tOP (nominal concentrations: 10, 50 or 100 μg l−1) or 17β-estradiol (E2; 0.5 μg l−1) in a continuous flow-through system for 3 weeks. A group of fish were exposed to 4-tOP (50 μg l−1) concomitantly with the anti-estrogen ZM 189,154 (20 μg g−1 week−1, i.p.). The Vtg concentration in plasma was measured by enzyme-linked immunosorbent assay. The testicular structure was examined by light microscopy and gamma-glutamyl transpeptidase (γ-GTP) activity was measured in the testes. The testicular localization of γ-GTP was analysed by enzyme histochemistry. A marked increase in the plasma Vtg concentration was observed after exposure to the actual concentration of 35 μg l−1 4-tOP (nominal concentration, 50 μg l−1), 63 μg l−1 4-tOP (nominal concentration, 100 μg l−1) or E2. Co-treatment with ZM 189,154 totally abolished the 4-tOP-dependent induction of Vtg synthesis. Exposure to 4-tOP or E2 caused a marked reduction in the testis mass and severely affected the testicular development and structure including the Sertoli cells (based on histology and γ-GTP activity), resulting in impairment of spermatogenesis and degeneration of lobular structures. Other cellular abnormalities such as accumulations of yellowish-brown pigmented cells and increased interstitial fibrosis in the testes was also observed in the exposed fish. In the groups exposed to the nominal concentrations of 50 or 100 μg l−1all fish had severely affected testes, while both normal, moderately and severely affected testes were found in the group exposed to the nominal concentration of 10 μg l−1. Co-treatment with ZM 189,154 abolished part of these 4-tOP-induced effects on the testicular growth and histological structure. The study demonstrates that an anti-estrogen can abolish effects on the testis caused by estrogenic chemicals, providing evidence that some of the effects are mediated by the estrogen receptor.