HEPATIC CYTOCHROME P4501A INDUCTION IN DAB (LIMANDA-LIMANDA) AFTER ORAL DOSING WITH THE POLYCHLORINATED BIPHENYL MIXTURE CLOPHEN A40

The flatfish dab (Limanda limanda) serves as an indicator species in p ollution monitoring programmes in the North Sea. The present study inv estigated the induction response of the monooxygenase system and haema tological changes in female dab after multiple administrations of a te chnical mixture of polychlorinated biphenyls (PCBs). Mature female dab were dosed with 1 mg of the PCB mixture Clophen A40 (Clo A40) in sunf lower oil every 6 weeks, with a maximum of three doses per fish. In al l PCB-administered groups, levels of cytochrome P4501A (CYP1A) protein , measured with a semi-quantitative ELISA method, and 7-ethoxyresorufi n O-deethylase (EROD) activity showed a three- to ninefold induction 1 4 d after dosing compared with control groups, smaller but also signif icant increases were observed in total cytochrome P450 (Sigma P450) le vels. Although the PCB concentrations and the corresponding toxic equi valent (TEQ) value in muscle tissue still increased after administrati on of the second and third dose of Clo A40, maximum responses of the E ROD activity were already reached after the first dose at a TEQ value for chlorinated biphenyls (CB-TEQ) of 2 ng/g lipid. The PCB patterns o f liver and muscle tissue of female dab from the central North Sea wer e found to be virtually identical. Hence, the use of PCB concentration s in muscle as a qualitative model for changes in the liver appears le gitimate. Haemoglobin concentrations were elevated after the third dos e of Clo A40, whereas haematocrit values and the mean corpuscular haem oglobin concentration (MCHC) between treated and control groups did no t differ.