CYP1A1-, CYP2B- and CYP3A-like proteins in rainbow trout (Oncorhynchus mykiss) liver: CYP1A1-specific down-regulation after prolonged exposure to PCB

Induction of cytochrome P450 1A (CYP1A) has been widely employed as a biomarker for exposure to halogenated aromatic hydrocarbons, such as co-planar PCB, in the aquatic environment. Recently, however, non-responsiveness to PCB has been reported in fish collected from heavily PCB-contaminated sites in North America and Europe. In a recent study, we investigated the CYP1A1 system in juvenile rainbow trout (Oncorhynchus mykiss) after an initial intra peritoneal injection of either carrier vehicle, 3-methylcholanthrene (3-MC) or a PCB mixture (Clophen A50) in a 20-week laboratory experiment. Furthermore, we showed that prolonged exposure to PCB seems to impair the inducibility of the CYP1A1 system in rainbow trout liver (Celander & Förlin, 1995). In the present study, immunoblot analyses confirms that this apparent down-regulation was specific to CYP1A1, while levels of CYP2B- and CYP3A-like proteins remained mainly unchanged.