Clarification of the Relationship Between Free Radical Spin Trapping and Carbon Tetrachloride Metabolism in Microsomal Systems

Abstract

It has been proposed that the C-phenyl- N-tert-butylnitrone/trichloromethyl radical adduct (PBN/ •CCl 3) is metabolized to either the C-phenyl- N-tert-butylnitrone/carbon dioxide anion radical adduct (PBN/ •CO 2 −) or the glutathione (GSH) and CCl 4-dependent PBN radical adduct (PBN/[GSH- •CCl 3]). Inclusion of PBN/ •CCl 3 in microsomal incubations containing GSH, nicotinamide adenine dinucleotide phosphate (NADPH), or GSH plus NADPH produced no electron spin resonance (ESR) spectral data indicative of the formation of either the PBN/[GSH- •CCl 3] or PBN/ •CO 2 − radical adducts. Microsomes alone or with GSH had no effect on the PBN/ •CCl 3 radical adduct. Addition of NADPH to a microsomal system containing PBN/ •CCl 3 presumably reduced the radical adduct to its ESR-silent hydroxylamine because no ESR signal was observed. The Folch extract of this system produced an ESR spectrum that was a composite of two radicals, one of which had hyperfine coupling constants identical to those of PBN/ •CCl 3. We conclude that PBN/ •CCl 3 is not metabolized into either PBN/[GSH- •CCl 3] or PBN/ •CO 2 − in microsomal systems.