Studies on the Influence of Polychlorinated Biphenyls (PCB) on Aquatic Organisms. VIII. Influence of PCB on Drug-Metabolizing Enzyme System in Carp

Abstract

The effect of Aroclor 1248 (PCB) on the hepatopancreatic microsomal enzymes of carp was examined. The carp were fed a diet containing 250 ppm PCB for 7 days, and activities of NADPH-cytochrome c reductase, NADH-cytochrome b5 reductase, aminopyrine N-demethylase, and aryl hydrocarbon hydroxylase, along with the amount of cytochrome P-450, cytochrome b5, and microsomal protein increased significantly by ingestion of PCB. These results showed that Aroclor 1248 induced hepatopancreatic drug-metabolizing enzymes of carp which are similar to hepatic enzymes in mammals. The induction, however, seemed to be a mixed type, also induced by phenobarbital and 3-methylcholanthrene. By measuring the substrate-binding difference spectra of hepatopancreatic microsomes from the carp pretreated with Aroclor 1248, the PCB was found to be bound to cytochrome P-450 in a "modified type II" pattern as classified by Schenkman and others. The spectral changes induced by hexobarbital and aniline, and an increase in the δ-aminolevulinic acid synthetase activity also suggested that Aroclor 1248 increased the synthesis of cytochrome P-450 in the carp hepatopancreas. SDS-polyacrylamide gel electrophoresis, further demonstrated that the hepatopancreatic microsomes contained four kinds of heme protein and that the synthesis of the heme was induced by treatment of the carp with Aroclor 1248.