CYP2E1-DEPENDENT BIOACTIVATION OF 1,1-DICHLOROETHYLENE IN MURINE LUNG- FORMATION OF REACTIVE INTERMEDIATES AND GLUTATHIONE CONJUGATES

We investigated the cytochrome P450-dependent metabolism of 1,1-dichlo roethylene (DCE) in murine lung microsomal incubations, The metabolite s were identified as their glutathione conjugates or hydrolyzed produc ts, analyzed by HPLC and quantified with [C-14]DCE, We determined the relative quantities of DCE metabolites formed in lung microsomal incub ations and compared them to those produced in liver. Furthermore, we u sed antibody inhibition experiments to investigate the CYP2E1-dependen t metabolism of DCE in lung, Our results demonstrated that reactive in termediates were generated from DCE in the lung microsomal incubations . The DCE epoxide (12.6 +/- 1.4 pmol/mg protein/min) was the major met abolite formed and was identified as two glutathione conjugates, 2-(S- glutathionyl) acetyl glutathione and 2-S-glutathionyl acetate. Lower l evels of the acetal of 2,2-dichloroacetaldehyde (3.6 +/- 0.25 pmol/mg protein/min) were detected. The ratio of acetal to DCE epoxide was hig her in lung (0.30 +/- 0.04) than in liver (0.12 +/- 0.02). Preincubati on of microsomes with a CYP2E1-inhibitory monoclonal antibody resulted in a maximum inhibition of 50% in the formation of both the acetal an d the glutathione conjugates derived from the DCE epoxide, These data demonstrated that lung CYP2E1 metabolizes DCE to reactive intermediate s of which the DCE epoxide is both the major metabolite formed and an efficient scavenger of glutathione, implicating it as an important tox ic species mediating DCE-induced lung cytotoxicity. (C) 1996 Academic Press, Inc.