In vivo formation and localization of 1,1-dichloroethylene epoxide in murine liver: identification of its glutathione conjugate 2-S-glutathionyl acetate.

The hepatotoxic effects induced by 1,1-dichloroethylene (DCE) are ascribed to cytochrome P-450 (CYP) 2E1-dependent formation of metabolites including 2,2-dichloroacetaldehyde and the DCE-epoxide. The DCE metabolites detected in incubations of liver microsomes are the acetal, the hydrate of 2,2-dichloroacetaldehyde, and the epoxide-derived GSH conjugates 2-S-glutathionyl acetyl glutathione ([B]) and 2-S-glutathionyl acetate ([C]). This study was undertaken to determine whether these DCE metabolites are also formed in vivo in murine liver. HPLC analysis of cytosol isolated from the livers of mice treated with [(14)C]DCE showed that [C] was the major conjugate formed, with lower levels of formation of [B]. The acetal was not detected in the cytosol. The formation of the epoxide-derived GSH conjugates was dose-dependent at 25 to 225 mg/kg DCE and occurred coincidentally with levels of covalent binding of DCE at the same doses. The acetal and conjugates [B] and [C] were also detected in bile collected from mice treated with DCE. Pretreatment of mice with buthionine sulfoximine decreased sulfhydryl levels and formation of conjugate [C], and increased DCE binding to liver proteins. In contrast, the levels of [C] and DCE binding were both reduced significantly in mice pretreated with the CYP2E1 inhibitor diallyl sulfone. Immunohistochemical studies indicated that protein adducts and conjugate [C] were localized in centrilobular hepatocytes and corresponded with the sites where CYP2E1 resided. Pretreatment with buthionine sulfoximine increased the amount of immunostaining. However, pretreatment with diallyl sulfone markedly decreased immunostaining for [C] in the hepatocytes. These results showed that 2,2-dichloroacetaldehyde and the epoxide are formed from DCE in vivo.