Long-term exposure effects in vitellogenin, sex hormones, and biotransformation enzymes in female carp in relation to a sewage treatment works

In the present study, the estrogenic response in the reproductive cycle of female carp, Cyprinus carpio, in relation to a sewage treatment works (STWs) was measured as: alterations in plasmatic and hepatic vitellogenin (VTG) content, plasma levels of testosterone (T) and estradiol (E2), and effects on key enzymes of phases I and II biotransformation, ethoxyresorufin O-deethylase (EROD) and glutathione S-transferase (GST). Low plasma VTG content in females collected 4 km downstream of an effluent discharge suggested possible estrogenic disturbances; however, hepatic VTG content and sex hormone levels did not mirror this. In fact, E2 and T largely fluctuated among fish, with individual variations even greater than among sampling stations or periods. This suggests that at moderately polluted sites, biological variations of female carp and genetic particularities are prevalent. Hepatic biotransformation enzymes, such as EROD, increased with increasing water temperature while, in contrast, GST was maximal at the lowest water temperature.