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Aryl radical formation during the metabolism of arylhydrazines by microsomes.
Gannett-PM; Shi-X; Lawson-T; Kolar-C; Toth-B
Chem Res Toxicol 1997 Dec; 10(12):1372-1377
Aryl radical formation during the microsomal metabolism of arylhydrazines was investigated. p-Methylphenylhydrazine (539446) (MePH) or p-(methoxymethyl)phenylhydrazine (MeOMePH) was incubated with rat liver microsomes or microsomes prepared from C50 cells, a murine keratinocyte line, for 45 minutes in the presence of 5,5'- dimethyl-1-pyrroline-N-oxide (DMPO) or N-tert-butyl-alpha- phenylnitrone (PBN) used as spin traps. The reaction mixtures were analyzed for formation of radicals by electron spin resonance (ESR) spectroscopy. ESR spectra of the products formed by the reaction of MePH in rat liver microsomes revealed only the presence of the hydroxyl-radical (OH) when DMPO was used as the spin trap. Incubation of MeOMePH with rat liver microsomes produced a number of trapped radicals with DMPO. OH and the p-(methoxymethyl)phenyl (MeOMeP) radical could be identified. Two other ESR peaks that may have been DMPO trapped hydroperoxy radicals derived from MeOMePH were also observed. Adding superoxide-dismutase to the mixture abolished these two peaks. Incubation of MePH and MeOMePH with C50 cell microsomes using DMPO as the spin trap produced OH and the methylphenyl radical in the case of MePH and the MeOMeP radical in the case of MeOMePH. The ESR spectral assignments for these radicals were confirmed when the reactions were run using PBN as the spin trap. The authors conclude that the ESR signal intensities for the radicals produced by the microsomal metabolism of MePH and MeOMePH parallel the ability of the two compounds to form C8-aryl- guanine adducts in DNA, as measured previously. This indicates that aryl radicals are formed during the metabolism of arylhydrazine and these radicals then react with DNA to form C8 adducts.
Aryls; Free-radicals; Genotoxic-effects; Hydroxyl-groups; Laboratory-animals; Animals; Animal-studies; Liver-disorders; Triazenes
Issue of Publication
Chemical Research in Toxicology
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Content source: National Institute for Occupational Safety and Health Education and Information Division