Cytochrome P4501A and associated mixed-function oxidase induction in fish as a biomarker for toxic carcinogenic pollutants in the aquatic environment

Polycyclic aromatic hydrocarbons (PAHs), dioxins, dibenzofurans, and polych lorinated biphenyls (PCBs) present in polluted environment induce cytochrom e P4501A (CYP1A) isozyme in fish, which in turn results in a marked increas ed production of carcinogenic metabolites from PAHs. The induction of hepat ic CYP1A in fish by certain classes of chemicals has been suggested as an e arly warning system, a "most sensitive biological response" for assessing e nvironmental contamination conditions. This has implications for human fish consumption, as well as for the health status of aquatic organisms. Correl ation between elevated CYP1A and altered steroid metabolism and decreased r eproductive success has been pointed out. The induction of CYP1A and associ ated enzyme activities has now been confirmed in a number of field studies. Cases where these biomarkers have been studied in field conditions will be presented. Special emphasis will be given to field studies in which the in duction of CYP1A activity, 7-ethoxyresonufin O-deethylase (EROD) activities and immunochemical detection of CYP1A in leaping mullet and common sole ar e used as a biomarker for PAH- and/or PCB-type pollutants along the Izmir B ay on the Aegean Sea.