Histological alternation and vitellogenin induction in adult rare minnow (Gobiocypris rarus) after exposure to ethynylestradiol and nonylphenol

Adult rare minnow (Gobiocypris rarus) were exposed to 0, 1, 5, and 25 ng/l (nominal concentrations) of 17α-ethynylestradiol (EE₂) and 3, 10, and 30 μg/l (nominal concentrations) of 4-nonylphenol (NP) under flow-through conditions for a period of 28 d. Low mortality was observed at 5 and 25 ng/l EE₂ and the growth of fish reduced significantly at 25 ng/l EE₂ compared to controls. However, the gonadosomatic indices (GSI) of male fish were significantly higher in 1 ng/l EE₂ treatments and in 10 and 30 μg/l NP treatments (p < 0.05). Renal somatic indices (RSI) of male fish in EE₂ treatments were significantly higher than those in controls (p < 0.05). In contrast, significantly decreased GSI and RSI of female fish could only be observed in 5 and 25 ng/l EE₂treatments (p < 0.05). Hepatosomatic indices (HSI) of male fish were significantly higher in 25 ng/l EE₂ treatments. However, significantly increased of HSI of female fish could only be observed in 1 ng/l EE₂ treatments. Plasma vitellogenin (VTG) induction could be observed in males after exposed to different concentrations of EE₂ and NP, and plasma VTG concentrations in females exposed to 5 and 25 ng/l EE₂ were also significantly higher than in controls (p < 0.05). At level higher than 5 ng/l EE₂ or 30 μg/l NP, hepatic tissue and renal tissue impairment of males could be observed. The pathological male liver was associated with a hypertrophy of hepatocytes and damages to cellar structure and accumulated eosinophilic material. Renal tissue showed different pathological effects which was reflected by accumulated eosinophilic material, hemorrhages within the kidney tubules and hypertrophy of the tubular epithelia. Also at these levels of exposure, feminization of male fish could be noticed and parts of males manifested the testis-ova phenomenon. Ovaries of female rare minnow in 25 ng/l EE₂ treatment group were degenerated. Therefore when exposed to EE₂ and NP even at environmental observed concentrations, adverse effects could occur in the reproductive system of adult fishes. The observed hepatic tissue and renal tissue impairment should be due to the induction and accumulation of VTG in organs, especially in males.