Vitellogenic effects of 17β-estradiol in male Chinese loach (Misgurnus anguillicaudatus)

Male Chinese loaches (Misgurnus anguillicaudatus) were exposed to 17β-estradiol (E₂) in the ambient water at nominal concentrations of 0.5, 1, 5 and 10 μg/L continuously for 8 weeks using a semi-static system. The gonadosomatic index (GSI), total plasma protein, total plasma calcium, magnesium and zinc, and plasma vitellogenin (Vtg) were determined as test endpoints. Our results indicate no significant changes in the GSI between exposed and control groups (P < 0.05). All exposure concentrations of E₂ dramatically induced the production of Vtg within 7 days. The vitellogenic response of male loach was time- and dose-dependent. At higher concentrations of E₂ (5 and 10 μg/L), total plasma protein, total plasma calcium, and total plasma magnesium presented a significant time- and dose-dependent increase, and the three parameters were significantly correlated with plasma Vtg. We conclude that Chinese loaches are sensitive to estrogenic compounds and may be chosen as potential sentinel species in field and laboratory studies. In addition, total plasma protein, total plasma calcium, and total plasma magnesium can be used as indirect indicators to predict Vtg levels in estrogenized Chinese loach.