The in vitro dechlorination of some polychlorinated ethanes

Chlorinated olefins were formed in vitro from hexachloroethane, pentachloroethane, and 1,1,1,2-tetrachloroethane by phenobarbital-induced rat liver microsomes. The production of tetrachloroethylene, trichloroethylene, and 1,1-dichloroethylene, respectively, was quantified by gas chromatographic analysis of headspace samples from the reaction vessels. The reaction showed a pH optimum of 7.0-7.5 under a nitrogen atmosphere; oxygen inhibited the reaction. The formation of olefins required NADPH and it was inhibited by SKF 525-A, metyrapone, and carbon monoxide. The reaction caused an increase in lipid peroxidation as measured by conjugated diene and malondialdehyde formation. The formation of olefins from these polychlorinated ethanes is apparently due to a cytochrome P-450-mediated vic-bisdechlorination reaction which may involve a free radical intermediate.