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Abstract
Vitellogenin (Vtg) induction in African sharptooth catfish (Clarias gariepinus) was assessed in order to develop a method for monitoring estrogenic pollution in African freshwater systems. Clarias gariepinus Vtg (Cg-Vtg) was purified from serum obtained from 17α-ethynylestradiol (EE2)-exposed fish and polyclonal antibodies against Cg-Vtg were raised. An enzyme-linked immunosorbent assay (ELISA) was developed and the induction and kinetics of Vtg were assessed in male fish in three different exposure trials using both natural estrogen (17α-estradiol [E2]) and synthetic EE2. Concentrations of EE2 in water and levels of EE2 conjugates in bile were quantified by liquid chromatography–mass spectrometry (LC-MS). In addition, co-administration of E2 and benzo[a]pyrene (BaP) were studied. Vtg was induced in all exposure trials and the maximum induction was observed 1 wk after exposure. Exposure of male C. gariepinus to 1.4, 2.7, and 13.9 μg/ml EE2 induced Vtg synthesis at all concentrations. BaP did not influence the Vtg kinetics. However, an increased rate of biliary excretion of EE2 was observed when BaP was additionally administered. In conclusion, Vtg is induced in male C. gariepinus after exposure to both E2 and EE2, rendering it a suitable biomarker for endocrine-disrupting chemicals in African freshwater systems.
This study was kindly funded by the Magne Lerheims stipend and the Norwegian Universities' Committee for Development Research and Education (NUFU) PRO 08/2002. We express our sincere thanks to Ingunn Samdal, Cosmas Andrea, Abel Mjema, and Hamza Mbena.