Polycyclic aromatic hydrocarbons (PAHs), dioxins, dibenzofurans, and polychlorinated biphenyls (PCBs) present in polluted environment induce cytochrome P4501A (CYP1A) isozyme in fish, which in turn results in a marked increased production of carcinogenic metabolites from PAHs. The induction of hepatic CYP1A in fish by certain classes of chemicals has been suggested as an early warning system, a "most sensitive biological response" for assessing environmental contamination conditions. This has implications for human fish consumption, as well as for the health status of aquatic organisms. Correlation between elevated CYP1A and altered steroid metabolism and decreased reproductive success has been pointed out. The induction of CYP1A and associated 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 induction of CYP1A activity, 7-ethoxyresorufin O-deethylase (EROD) activities and immunochemical detection of CYP1A in leaping mullet and common sole are used as a biomarker for PAH- and/or PCB-type pollutants along the Izmir Bay on the Aegean Sea.

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Quercetin, resveratrol, naringenin, hesperidin, and rutin are phenolic compounds/flavonoids that may have roles in the reduction of cancer susceptibility. In this study, in vitro modulatory effects of them were studied on liver CYP1A1 associated 7-ethoxyresorufin-O-deethylase (EROD) activity and glutathione S-transferase (GST) activity of leaping mullet (Liza saliens). All of the phenolic compounds/flavonoids used exerted an inhibitory effect on both EROD and GST activities of fish. Quercetin, resveratrol, hesperidin, and rutin were found to inhibit EROD activity in a competitive manner; on the other hand, naringenin was found to inhibit EROD activity in a noncompetitive manner. Ki values of quercetin, resveratrol, naringenin, hesperidin, and rutin were calculated from Dixon plots as 0.12 μM, 0.67 μM, 2.63 μM, 18 μM and 0.1 mM, respectively. Resveratrol, quercetin, and hesperidin were found to inhibit GST activity in a competitive manner; on the other hand, rutin and naringenin were found to inhibit GST activity in a mixed-type manner. Ki values of resveratrol, quercetin, hesperidin, naringenin, and rutin were calculated from Dixon plots as 3.2 μM, 12.5 μM, 45 μM, 128 μM, and 150 μM, respectively. The results suggest that quercetin and resveratrol containing foods are effective in the prevention and treatment of cancer.