CLARIFICATION OF THE RELATIONSHIP BETWEEN FREE-RADICAL SPIN-TRAPPING AND CARBON-TETRACHLORIDE METABOLISM IN MICROSOMAL SYSTEMS

It has been proposed that the C-phenyl-N-tert-butylnitrone/trichlorome thyl radical adduct (PBN/(CCl3)-C-.) is metabolized to either the C-ph enyl-N-tert-butylnitrone/carbon dioxide anion radical adduct (PBN/(CO2 -)-C-.) or the glutathione (GSH) and CCl4-dependent PBN radical adduct (PBN/[GSH-(CCl3)-C-.]). Inclusion of PBN/(CCl3)-C-. in microsomal inc ubations containing GSH, nicotinamide adenine dinucleotide phosphate ( NADPH), or GSH plus NADPH produced no electron spin resonance (ESR) sp ectral data indicative of the formation of either the PBN/[GSH-(CCl3)- C-.] or PBN/(CO2-)-C-. radical adducts. Microsomes alone or with GSH h ad no effect on the PBN/(CCl3)-C-. radical adduct. Addition of NADPH t o a microsomal system containing PBN/(CCl3)-C-. 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 spectru m that was a composite of two radicals, one of which had hyperfine cou pling constants identical to those of PBN/(CCl3)-C-.. We conclude that PBN/(CCl3)-C-. is not metabolized into either PBN/[GSH-(CCl3)-C-.] or PBN/(CO2-)-C-. in microsomal systems. (C) 1998 Elsevier Science Inc.