Effects of 17a-Ethynylestradiol on Hepatosomatic Index, Plasma Vitellogenin Levels and Liver Glutathione-S-Transferase Activity in Lake Van Fish (Chalcalburnus tarichi Pallas, 1811)

17a-ethynylestradiol (EE2), a synthetic estrogen used in birth control pills, has frequently been detected in aquatic environments. In the present study, male and female individuals (3+ ages) of Chalcalburnus tarichi, an endemic cyprinid fish living in the Lake Van basin located in the eastern Anatolia region of Turkey, were exposed to nominal concentrations of 1, 10, and 100 ng/L EE sub(2) for 32 days at semistatic daily renewal conditions. After exposure, plasma vitellogenin (Vtg), hepatosomatic index (HSI), and liver glutathione-5-transferase (GST) activity were examined. Plasma Vtg concentrations exhibited significant inductions in all doses of EE sub(2) in both sexes. HSI did not change at the 1 and 10 ng/L EE sub(2) concentrations; it, however, significantly increased after 100 ng/EE sub(2) exposure in males and females. Liver GST activity significantly increased in females at the 1 ng/L EE sub(2) exposure, whereas it did not change in males. On the other hand, GST activity was inhibited in both sexes at the 10 and 100 ng/L EE sub(2) exposures. The results of this study indicate that C. tarichi is highly suspectible to EE sub(2) and its detoxification capability may be weakened by EE sub(2)-inhibiting phase II enzyme, GST.