A Spin Trap Study on Anaerobic Dehalogenation of Halothane by a Reconstituted Liver Microsomal Cytochrome P.450 Enzyme System1

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Abstract
In the presence of a spin trapping reagent, N-tert-butyl-α-phenylnitrone, anaerobic incubation of halothane (2-bromo-2-chloro-1,1,1-trifluoroethane) with a reconstituted cytochrome P-450 enzyme system of rabbit liver microsomes exhibited an electron spin resonance spectrum containing signals of a nitroxide radical, and all components of the reconstituted system were necessary to produce the nitroxide radical. Formation of 2-chloro-1,1,1-trifluoroethane, the product of anaerobic dehalogena-tion of halothane by the reconstituted system, was inhibited by N-tert-butyl-α-phenylnitrone. These results indicate that a radical intermediate of halothane is produced during the anaerobic dehalogenation reaction, and that the radical is trapped by N-tert-butyl-α-phenylnitrone to form a N-tert-butyl-α-phenylnitrone radical adduct.