REACTION OF GLUTATHIONE WITH THE ELECTROPHILIC METABOLITES OF 1,1-DICHLOROETHYLENE

1-1-Dichloroethylene (DCE) requires cytochrome P450-catalyzed bioactiv ation to electrophilic metabolites (1,1-dichloroethylene oxide, 2-chlo roacetyl chloride and 2,2-dichloroacetaldehyde) to exert its cytotoxic effects. In this investigation, we examined the reactions of these me tabolites with glutathione by spectroscopic and chromatographic techni ques. In view of the extreme reactivity of 2-chloroacetyl chloride, pr imary reactions are likely to include alkylation of cytochrome P450, c onjugation with GSH to give S-(2-chloroacetyl)glutathione, or hydrolys is to give 2-chloroacetic acid. Our results showed conjugation of GSH with 1,1-dichloroethylene oxide, through formation of the mono- and di -glutathione adducts, 2-S-glutathionyl acetate and 2-(S-glutathionyl) acetyl glutathione, respectively. The observed equilibrium constant be tween the hydrate of 2,2-dichloroacetaldehyde and S-(2,2-dichloro-1-hy droxy)ethylglutathione was estimated from H-1-NMR experiments to be 14 +/- 2 M(-1). Thus, 2,2-dichloroacetaldehyde is unlikely to make a sig nificant contribution to GSH depletion as GSH concentrations above nor mal physiological levels would be necessary to form significant amount s of S-(2,2-dichloro-1-hydroxy)ethylglutathioe. We also compared the f ormation of the glutathione conjugates in rat and mouse liver microsom es using C-14-DCE. The results demonstrated a species difference; the total metabolite production was 6-fold higher in microsomes from mice, compared with samples from rat. Production of DCE metabolites in hepa tic microsomes from acetone-pretreated mice was 3-fold higher than tho se from untreated mice suggesting a role for P450 2E1 in DCE bioactiva tion. These results indicate that the epoxide is the major metabolite of DCE that is responsible for GSH depletion, suggesting that it may b e involved in the hepatotoxicity evoked by DCE. Furthermore, this meta bolite is formed to a greater extent in mouse than in rat liver micros omes and this difference may underlie the enhanced susceptibility foun d in the former species.