Analytical methodology for the identification of estrogenic contaminants in fish bile

Effluents from wastewater treatment works (WwTWs) contain estrogenic contaminants that can cause feminised responses in fish. In order to assess the identity of estrogenic contaminants taken up by fish exposed to effluents, an analytical method was developed to detect estrogenic substances in fish bile, where many xenobiotics are excreted and concentrated. Estrogenic metabolites in bile were deconjugated using enzymatic hydrolysis and the estrogenic activity was determined using a yeast estrogen receptor transcription screen (YES). Hydrolysed samples were concentrated by solid-phase extraction (SPE) prior to fractionation by reversed-phase high-performance liquid chromatography (HPLC). Active HPLC fractions were detected by YES assay and analysed by gas chromatography–mass spectrometry (GC–MS) after trimethylsilylation. The method was validated using bile samples from immature female rainbow trout, which had been exposed to either tap water or an undiluted estrogenic effluent for 10 days. Hydrolysis of bile from effluent-exposed fish was complete within 16 h and most of the estrogenic activity in the bile was released by β-glucuronidase rather than sulfatase or β-glucosidase treatment. The estrogenic activity of hydrolysed bile from effluent-exposed fish ranged between 530 and 1440 ng E2eq/mL and was 17–48-fold greater than the activity of bile from reference fish exposed to tap water. The estrogenic activity of bile samples decreased with time in storage (at −70 °C by 7% per month). The recovery of estrogenic activity from SPE was 96 ± 7% (mean ± SD), from HPLC fractionation 87 ± 7% and for the whole method 81 ± 7% (n = 7). 17β-Estradiol, estrone, 17α-ethinylestradiol, nonylphenol and short-chain nonylphenol polyethoxylates were all identified from GC–MS analysis of active HPLC fractions of bile from effluent-exposed trout, whereas only 17β-estradiol was detected in bile from fish exposed to tap water. There were also several other minor estrogenic components, at present unidentified, in bile of effluent-exposed fish. The work shows that fractionation of fish bile is a useful approach to identifying mixtures of estrogenic contaminants taken up by fish from WwTW effluents and has the potential for application in the detection of other endocrine disrupting chemicals in fish tissues.