TIME-DEPENDENT AND DOSE-DEPENDENT BIOMARKER RESPONSES IN FLOUNDER (PLATICHTHYS-FLESUS L) EXPOSED TO BENZO[A]PYRENE, 2,3,3',4,4',5-HEXACHLOROBIPHENYL (PCB-156) AND CADMIUM

Responses in flounder (Platichthys flesus) towards benzo [a]pyrene (Ba P), 2,3,3',4,4',5-hexachlorobiphenyl (PCB-156), and cadmium (Cd) were investigated in time-course and dose-response studies of selected biom arkers. Measurements of biliary fluorescent BaP metabolites and hepati c concentrations of PCB-156 and cadmium showed that the injected toxic ants were rapidly mobilized from the muscle to the liver, but a depot effect was indicated in the highest dose groups of BaP and PCB-156 (12 mg kg(-1) bodyweight). Clearest biomarker responses were found in the induction of hepatic cytochrome P450 1A (CYP1A) enzymes as a response towards BaP and PCB-156 exposure. Maximum induction of CYP1A dependen t 7-ethoxyresorufin-O-deethylase (EROD) activity was observed after 2 and 8 days in BaP and PCB-156-treated flounder, respectively. Positive dose-effect relationships were observed towards both compounds, but t he CYP1A induction was move persistent with PCB exposure than with BaP exposure. In Cd-exposed fish, the hepatic lever of metallothionein re sponded more slowly with highest levels observed after 16 days in the time-study, in the combined BaP + Cd treatment, the CYP1A induction wa s only slightly suppressed. Aspartate aminotransferase in serum appear ed to be responsive towards BaP, but also towards the acetone vehicle in controls in the first part of the exposure period. Hematocrit as we ll as hepatic activities of aldrin epoxidase, glutathione S-transferas e, and UDP-glucuronyl transferase were not responsive to any treatment in the present study. in general, the results demonstrate that select ed biomarkers in flounder are responsive to PAH, PCB, and heavy metal pollutant exposure, indicating the applicability of this species in fu ture environmental pollution monitoring programmes.