INTERACTION OF 2,2',4,4',5,5'-HEXACHLOROBIPHENYL WITH HEPATIC CYTOCHROME P-4501A IN RAINBOW-TROUT (ONCORHYNCHUS-MYKISS)

Di-ortho polychlorinated biphenyls (PCBs) are prominent environmental contaminants and their biological activity in fish may be more signifi cant than previously thought. Four weeks after intraperitoneal (ipi in jection with 50 or 250 mu g 2,2',4,4',5,5'-hexachlorobiphenyl (2HxCB)/ g fish, rainbow trout livers were removed and frozen at -80 degrees C or microsomes were prepared. Microsomal ethoxyresorufin O-deethylase ( EROD) activity was approximately one and two orders of magnitude great er than controls in fish treated with 50 and 250 mu g 2HxCB/g fish, re spectively. Cytochrome P4501A (CYP1A) Western immunoblot relative opti cal density increased with 2HxCB dose. Hepatic CYP1A1 mRNA levels were approximately threefold greater in fish treated with 250 mu g 2HxCB/g fish than in controls, while hepatic CYP1A1 mRNA levels in fish treat ed with 50 mu g 2HxCB/g fish were not significantly induced. There was no increase of CYP1A3 mRNA in 2HxCB-treated fish. The study showed 2H xCB induced hepatic EROD activity, CYP1A protein, and CYP1A1 mRNA cont ent in rainbow trout.