Evidence of direct generation of oxygen free radicals from heterocyclic amines by NADPH/cytochrome P-450 reductase in vitro

Jpn J Cancer Res. 1992 Nov;83(11):1204-9. doi: 10.1111/j.1349-7006.1992.tb02746.x.

Abstract

Highly purified cytochrome P-450 reductase (also called cytochrome c reductase; EC 1.6.2.4.) and NADPH were used to generate superoxide radical (O2.-) from 11 different heterocyclic amines (HCAs) as identified by electron spin resonance spectroscopy using the spin trapping method with 5,5-dimethyl-1-pyrroline N-oxide (DMPO). The signal intensity of DMPO-OOH(-O2-) (i.e., the DMPO spin adduct of O2.-) was strongest for 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ). The O2.- generation with HCAs decreased in the following order: 2-amino-3,8-dimethyl-imidazo[4,5-f]quinoxaline (MeIQx) = 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) > 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline (diMeIQx) > or = other HCAs; O2.- generation was lowest with 2-amino-3-methyl-9H-pyrido[2,3-b]indole .CH3COOH (MeA alpha C). By using Lineweaver-Burk plots, Km values of cytochrome P-450 reductase for mitomycin C, IQ, and MeIQ were determined to be 1.60 x 10(-6) M, 1.97 x 10(-5) M, and 2.83 x 10(-6) M, respectively. The present findings have important implications for carcinogenesis because of the known effect of oxygen radicals on cell proliferation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amines / metabolism*
  • Cyclic N-Oxides / metabolism
  • Cytochrome P-450 Enzyme System / metabolism
  • DNA / drug effects
  • DNA / genetics
  • Electron Spin Resonance Spectroscopy
  • Heterocyclic Compounds / metabolism*
  • Hydroxylation
  • Kinetics
  • Mixed Function Oxygenases / metabolism
  • Mutagenicity Tests
  • Mutagens / metabolism
  • NADP / metabolism
  • NADPH-Ferrihemoprotein Reductase / metabolism*
  • Pentetic Acid / metabolism
  • Quinolines / metabolism
  • Quinoxalines / metabolism
  • Reactive Oxygen Species / metabolism*
  • Superoxides / metabolism

Substances

  • Amines
  • Cyclic N-Oxides
  • Heterocyclic Compounds
  • Mutagens
  • Quinolines
  • Quinoxalines
  • Reactive Oxygen Species
  • Superoxides
  • NADP
  • 5,5-dimethyl-1-pyrroline-1-oxide
  • 2-amino-3,8-dimethylimidazo(4,5-f)quinoxaline
  • Pentetic Acid
  • DNA
  • Cytochrome P-450 Enzyme System
  • Mixed Function Oxygenases
  • NADPH-Ferrihemoprotein Reductase
  • 2-amino-3,4-dimethylimidazo(4,5-f)quinoline