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Vol. 290, Issue 3, 1299-1306, September 1999
Department of Anatomy and Cell Biology, Queen's University,
Kingston, Ontario, Canada
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
[14C]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.
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