DIFFERENCES IN CYP1A RESPONSE BETWEEN FLOUNDER (PLATICHTHYS-FLESUS) AND PLAICE (PLEURONECTES-PLATESSA) AFTER LONG-TERM EXPOSURE TO HARBOR DREDGED SPOIL IN A MESOCOSM STUDY

Flounder (Platichthys flesus) and plaice (Pleuronectes platessa) were exposed to three different levels of pollution involving contaminants from harbour dredged spoil in a large-scale mesocosm study lasting 30 months. Exposure of fish to PCBs and PAEs was estimated from liver con centrations of CB-153 and biliary level. of 1-OH Wrens in flounder. Bo th marker compounds were significantly elevated in fish from the pollu ted mesocosms in comparison to the reference mesocosm. Of the three pa rameters used to characterise CYP1A induction in flounder. only CYP1A- mRNA in female fish was significantly induced by pollution. However. s ignificant induction of EROD activity and immunochemically measured CY P1A protein content was observed in plaice. To investigate in more det ail the apparent lack of CYP1A induction. a parallel experiment was ru n in which flounder were injected with a single i.p. injection of benz o[a]pyrene (BaP) and sacrificed after 48 hours. Since this approach di d result in significant induction of all the parameters used to charac terise CYP1A induction (EROD, CYP1A, CYP1A mRNA), it appears that exte rnal. factors may have prevented induction in the mesocosm experiments . Down-regulating effects of the possible presence of a compound with oestrogenic activity, or altered membrane-CYP1A or membrane-receptor i nteraction. could have contributed to this apparent lack of response, despite the intrinsic ability of flounder to increase CYP1A levels aft er exposure to a model Inducer (BaP). Copyright (C) 1996 Elsevier Scie nce Ltd