Effects of chlorinated diphenyl ethers on the mixed-function oxidases and ultrastructure of rat and trout liver

The effects of chlorinated diphenyl ethers (CDEs) on hepatic mixed-function oxidase (MFO) activities and ultrastructure were examined in the rat and trout after ip administration of 100 mg/kg/day of 4-chlorodiphenyl ether (4-CDE), 2,4-dichlorodiphenyl ether (2,4-diCDE), 2,4,4'-trichlorodiphenyl ether (2,4,4'-triCDE), or 2,4,5,4'-tetrachlorodiphenyl ether (2,4,5,4'-tetraCDE) for 3 days. The 4-CDE, 2,4-diCDE, and 2,4,4'-triCDE pretreatments did not alter significantly the MFO activities of trout liver; however, 2,4,5,4'-tetraCDE pretreatment increased significantly the hepatic cytochrome b5 content and 7-ethoxycoumarin O-deethylase activity of trout liver. No histological changes were observed in the hepatocytes of trout treated with any of the CDEs. Pretreatment of rats with 4-CDE and 2,4-diCDE also did not alter significantly the MFO activities of the liver. In contrast, pretreatment of rats with 2,4,4'-triCDE and 2,4,5,4'-tetraCDE increased significantly hepatic MFO activities and also caused a proliferation of smooth endoplasmic reticulum in the liver. 2,4,4'-triCDE and 2,4,5,4'-tetraCDE appear to be a phenobarbital-type inducer and a mixed-type inducer of rat liver MFO activity, respectively.