Superoxide radical generation from heterocyclic amines.
Highly purified cytochrome P-450 reductase (also called cytochrome C reductase; EC 1.6.2.4.) and NADPH were found to generate superoxide radical (O2.-) from 11 different heterocyclic amines (HCAs) as identified by electron spin resonance spectroscopy (ESR) 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). O2.- generation with HCAs was decreased in the following order: 2-amino-3,8-dimethylimidazo[4,5-f]-quinoxaline (MeIQx) = 2-amino-3-methylimidazo[4,5-fl-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 N-hydroxyl derivative of 3-amino-1-methyl-5H-pyrido[4,3-b]-indole-HCI-CH3COOH (Trp-P-2), which is considered to be a key intermediate in the reaction of Trp-P-2 with cytochrome P-450 systems, yielded very little generation of O2.-. Because of the known presence of cytochrome P-450 reductase in the cell at significant amount, the present findings are an important implication for carcinogenesis and tumor promotion due to the known effect of oxygen radicals on promotion/progression, cell kill and proliferation.
Maeda
H
H
Department of Microbiology, Kumamoto University School of Medicine, Japan.
Sato
K
K
Akaike
T
T
D000588:Amines / Q000378:metabolism* / Q000633:toxicity; D000818:Animals; D002273:Carcinogens / Q000378:metabolism* / Q000633:toxicity; D003497:Cyclic N-Oxides; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods; D006571:Heterocyclic Compounds / Q000378:metabolism* / Q000633:toxicity; D006801:Humans; D007700:Kinetics; D008862:Microsomes, Liver / Q000201:enzymology; D009152:Mutagenicity Tests; D009153:Mutagens / Q000378:metabolism* / Q000633:toxicity; D009245:NADH Dehydrogenase / Q000378:metabolism*; D009249:NADP / Q000378:metabolism; D011804:Quinolines / Q000378:metabolism / Q000633:toxicity; D011810:Quinoxalines / Q000378:metabolism / Q000633:toxicity; D051381:Rats; D012486:Salmonella typhimurium; D013113:Spin Labels; D013481:Superoxides / Q000378:metabolism* / Q000633:toxicity
D000588:Amines; D002273:Carcinogens; D003497:Cyclic N-Oxides; D006571:Heterocyclic Compounds; D009153:Mutagens; D011804:Quinolines; D011810:Quinoxalines; D013113:Spin Labels; D013481:Superoxides; C029216:2-amino-3-methylimidazo(4,5-f)quinoline; D009249:NADP; C017245:5,5-dimethyl-1-pyrroline-1-oxide; C036990:2-amino-3,8-dimethylimidazo(4,5-f)quinoxaline; D009245:NADH Dehydrogenase