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  • Title: Structure-dependent induction of CYP2B1/2 by 3-methylsulfonyl metabolites of polychlorinated biphenyl congeners in rats.
    Author: Kato Y, Haraguchi K, Tomiyasu K, Hiroyuki Saito, Isogai M, Masuda Y, Kimura R.
    Journal: Environ Toxicol Pharmacol; 1997 Jun 06; 3(2):137-44. PubMed ID: 21781771.
    Abstract:
    The effects of eleven 3-methylsulfonyl (3-MeSO(2))-metabolites of polychlorinated biphenyl (PCB) congeners (which were reported to remain in Swedish mother's milk and Japanese Yusho patient's tissues) and their two structurally similar 3-MeSO(2)-PCBs on the hepatic drug-metabolizing enzyme activities were compared with those of phenobarbital (PB) and 3-methylcholanthrene (3-MC).The induction profile of the drug-metabolizing enzymes, CYP2B1 and CYP2B2 in the hepatic microsomes of rats treated with nine 3-MeSO(2) derivatives, namely 3-MeSO(2)-2,4',5-trichlorobiphenyl, 3-MeSO(2)-2,2',4',5-tetrachlorobiphenyl (3-MeSO(2)-2,2',4',5-tetraCB), 3-MeSO(2)-2,2',5,5'-tetraCB, 3-MeSO(2)-2,3',4',5-tetraCB, 3-MeSO(2)-2,2',3',4',5-pentachlorobiphenyl (3-MeSO(2)-2,2',3',4',5-pentaCB), 3-MeSO(2)-2,2',4',5,5'-pentaCB, 3-MeSO(2)-2,2',3',4',5,5'-hexachlorobiphenyl (3-MeSO(2)-2,2',3',4',5,5'-hexaCB), 3-MeSO(2)-2,2',3',4',5,6-hexaCB and 3-MeSO(2)-2,2',4',5,5',6-hexaCB, was similar to that of rats treated with PB, but was different from that of rats treated with 3-MC. These findings indicate that 3-MeSO(2) metabolites derived from nine PCBs are PB-type inducers of microsomal drug-metabolizing enzymes. The relative inducing potencies of 3-MeSO(2) derivatives on the hepatic drug-metabolizing enzyme activities differed with the extent of chlorination and the positions of chlorine substituent on the phenyl rings. The results of present study show that the structure-CYP2B1/2 induction relationship exists for the 3-MeSO(2) derivatives studied. The inducing abilities of 3-MeSO(2)-2,2',4',5-tetraCB and 3-MeSO(2)-2,2',4',5,5'-pentaCB (2 μmol/kg) on the content of cytochrome P450 were higher than those of 2,3',4,4',5-pentaCB (mono-ortho-substituted PCB) (80 μmol/kg), 3,3',4,4'-tetraCB (coplanar PCB) (80 μmol/kg) and 3,3',4,4',5-pentaCB (coplanar PCB) (0.5 μmol/kg). The inducing effects of the administration of 3-MeSO(2)-2,2',4',5-tetraCB and 3-MeSO(2)-2,2',4',5,5'-pentaCB at 2 μmol/kg on the contents of total cytochrome P450, CYP2B1 and CYP2B2 corresponded to those of PB at 431 μmol/kg twice at a 24 h interval. It is noticeable that 3-MeSO(2)-2,2',4',5-tetraCB and 3-MeSO(2)-2,2',4',5,5'-pentaCB have highly potent PB-type inducing activity on drug-metabolizing enzyme systems.
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