Biosynthesis of S-(2-chloro-1,1,2-trifluoroethyl)glutathione in rat and human hepatocytes and in Hep G2 cells.
Chlorotrifluoroethene is nephrotoxic in rats, and glutathione S-transferase-catalyzed S-(2-chloro-1,1,2-trifluorethyl)glutathione (CTFG) formation is the initial step in its bioactivation. CTFG biosynthesis and the activities of cytosolic and microsomal glutathione S-transferases were measured in rat and human hepatocytes and in human hepatoma-derived Hep G2 cells. Hepatocytes of > or = 88% viability were obtained from rat or human liver slices by collagenase or collagenase+dispase digestion, respectively. Hep G2 cells were grown in modified Earle's medium supplemented with 10% (v/v) fetal calf serum. Cells and subcellular fractions were exposed to chlorotrifluoroethene, and CTFG formation was quantified by HPLC. Both human liver and Hep G2 cell subcellular fractions catalyzed CTFG formation, and human and rat microsomal fractions exhibited higher specific activities than cytosolic fractions with chlorotrifluoroethene as the substrate. Time-dependent formation of CTFG was observed in all cell preparations. The presence of microsomal glutathione S-transferase was demonstrated by Western blotting with antimicrosomal glutathione S-transferase antibodies in rat and human liver tissue and in Hep G2 cells. Cytosolic and microsomal glutathione S-transferase activities were lower in Hep G2 cells than in rat and human liver tissues. These results demonstrate that human hepatocytes and Hep G2 cells are competent to synthesize CTFG and that Hep G2 cells may provide a useful model for studying human liver-catalyzed glutathione S-conjugate formation.
Tanaka
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Toxicology Laboratory, Mitsubishi Kasei Corporation.
Anders
M W
MW
D000818:Animals; D015153:Blotting, Western; D017402:Chlorofluorocarbons / Q000494:pharmacology; D003545:Cysteine / Q000378:metabolism; D005978:Glutathione / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism; D019803:Glutathione Disulfide; D006801:Humans; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008114:Liver Neoplasms, Experimental / Q000378:metabolism*; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D012995:Solubility; D013347:Subcellular Fractions / Q000187:drug effects / Q000378:metabolism; D014407:Tumor Cells, Cultured
D017402:Chlorofluorocarbons; C047567:S-(2-chloro-1,1,2-trifluoroethyl)glutathione; C016304:chlorotrifluoroethylene; D005978:Glutathione; D003545:Cysteine; D019803:Glutathione Disulfide