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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In this study, feral leaping mullet (Liza saliens) liver cytosolic glutathione S-transferases (GSTs) were investigated and characterized using 1-chloro-2,4-dinitrobenzene (CDNB) and ethacrynic acid (EA) as substrates. The average GST activities towards CDNB and EA were found to be 1365 +/- 41 and 140 +/- 20 nmol/min per mg protein, respectively. The effects of cytosolic protein amount and temperature ranging from 4 to 70 degrees C on enzyme activities were examined. While both activities towards CDNB and EA showed similar dependence on protein amount, temperature optima were found as 37 and 42 degrees C, respectively. In addition, the effects of pH on GST-CDNB and -EA activities were studied and different pH activity profiles were observed. For both substrates, GST activities were found to obey Michaelis-Menten kinetics with apparent V(max) and K(m) values of 1661 nmol/min per mg protein and 0.24 mM and 157 nmol/min per mg protein and 0.056 mM for CDNB and EA, respectively. Distribution of GST in Liza saliens tissues was investigated and compared with other fish species. Very high GST activities were measured in tissues from Liza saliens such as liver, kidney, testis, proximal intestine, and gills. Moreover, our results suggested that GST activities from Liza saliens would be a valuable biomarker for aquatic pollution.

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