Hepatic microsomal desulfuration and dearylation of chlorpyrifos and parathion in fingerling channel catfish: lack of effect from Aroclor 1254

Channel catfish were treated intraperitoneally with 100 mg Aroclor 1254/kg body weight and sacrificed at 96 h to observe the effects of this cytochrome P450 1A (CYP1A) inducer on chlorpyrifos and parathion metabolism. In the initial experiment, hepatic microsomal ethoxyresorufin-O-deethylase (EROD) activity of the Aroclor-treated fish was significantly induced but no effects on desulfuration or dearylation of chlorpyrifos or parathion were evident. In the second experiment, Aroclor 1254 did not alter total hepatic microsomal P450s content, but significantly induced hepatic EROD and CYP1A. There were no evident effects to other hepatic CYP isoforms recognized by anti-trout CYP2K1, CYP2M1 and CYP3A27. These experiments indicate that Aroclor 1254 did not induce the P450s responsible for metabolism of the phosphorothionate insecticides.