Induction of vitellogenin mRNA in juvenile Chinese sturgeon (Acipenser sinensis Gray) treated with 17β-estradiol and 4-nonylphenol

It has been demonstrated that 4-nonylphenol (4-NP) exerts estrogenic effects in diverse fishes. The present study investigated the effects of 4-NP on Chinese sturgeon (Acipenser sinensis Gray) vitellogenin (VTG) gene expression. By reverse transcription-polymerase chain reaction (RT-PCR) using degenerate primers, a 462-base pair fragment of Chinese sturgeon VTG, corresponding to a 154-amino acid sequence, was amplified and sequenced. This sequence exhibited 152/154 identity to the amino acid sequence of white sturgeon (A. transmontano) VTG. Conventional RT-PCR and quantitative real-time RT-PCR were established and used to study the VTG and P-actin gene expression in the liver of juvenile Chinese sturgeon injected three times with 17 beta-estradiol (5 mg/kg body wt/week) or 4-NP (10 or 100 mg/kg/week) in the course of three weeks. Significant induction of VTG gene expression was detected in all treated groups, and no VTG mRNA was detected in the control group. The ratio of VTG to beta-actin analyzed from the results of quantitative real-time RT-PCR reached 0.041 +/- 0.024 (mean SD) in the group receiving 10 mg/kg/week of 4-NP and 4.51 +/- 1.68 in the group receiving 100 mg/kg/week of 4-NP. Chemical analysis of 4-NP showed that the concentrations of 4-NP in the 10 mg/kg/week group and the 100 mg/kg/week group were 2.78 +/- 2.41 and 31.38 +/- 0.26 mu g/g wet weight, respectively. Compared with the 4-NP concentrations (0.8-1.92 mu g/g wet wt) in fish from the Yangtze River, China, a potential hazard exists regarding 4-NP in Chinese sturgeon. These results represent the first indication of the risk of endocrinedisrupting chemicals for Chinese sturgeon.