title: Superoxide generation by the respiratory chain of tumor mitochondria.
abstract: O2-. generation by the succinate oxidase segment of the respiratory chain of mitochondria and submitochondrial particles from hepatoma 22a and hepatoma Zajdela has been studied with the use of the Tiron method. In the presence of succinate, superoxide generation is induced by antimycin, 2-n-4-hydroxyquinoline N-oxide or funiculosin, and is inhibited by mucidin, myxothiazol or cyanide. The rate of O2-. generation in the antimycin-inhibited state is maximal at the [succinate]/[fumarate] ratio of 1:10 and diminishes at more positive and more negative redox potentials. These characteristics of O2-.-generation are the same as observed earlier in submitochondrial particles from normal tissues. Accordingly, the mechanism of superoxide production is suggested to be the same in tumor and normal mitochondria, namely, autoxidation of the unstable ubisemiquinone in the ubiquinol-oxidizing centre o of cytochrome bc1 complex. With respect to the rate of O2-. generation, the hepatoma mitochondrial membranes are approximately twice as active as bovine heart submitochondrial particles and exceed those from rat liver by more than one order of magnitude.
authors.affiliation: A.N. Belozersky Laboratory of Molecular Biology and Bioorganic Chemistry, M.V. Lomonosov Moscow State University, U.S.S.R.
authors.forename: A A
authors.initials: AA
authors.lastname: Konstantinov
authors.forename: A V
authors.initials: AV
authors.lastname: Peskin
authors.lastname: Popova EYu
authors.forename: G B
authors.initials: GB
authors.lastname: Khomutov
authors.forename: E K
authors.initials: EK
authors.lastname: Ruuge
mesh_terms: D014013:1,2-Dihydroxybenzene-3,5-Disulfonic Acid Disodium Salt; D000818:Animals; D000880:Anthraquinones / Q000494:pharmacology; D000968:Antimycin A / Q000031:analogs & derivatives / Q000494:pharmacology; D016227:Benzoquinones; D004578:Electron Spin Resonance Spectroscopy; D004579:Electron Transport / Q000187:drug effects; D005609:Free Radicals; D006912:Hydroxyquinolines / Q000494:pharmacology; D007700:Kinetics; D008114:Liver Neoplasms, Experimental / Q000378:metabolism*; D008297:Male; D051379:Mice; D008809:Mice, Inbred C3H; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism*; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000378:metabolism; D011809:Quinones / Q000378:metabolism; D051381:Rats; D013367:Submitochondrial Particles / Q000378:metabolism; D013386:Succinates / Q000494:pharmacology; D019802:Succinic Acid; D013481:Superoxides / Q000378:metabolism*
chemical_list: D000880:Anthraquinones; D016227:Benzoquinones; D005609:Free Radicals; D006912:Hydroxyquinolines; D011809:Quinones; D013386:Succinates; D013481:Superoxides; C032456:antimycin; C010494:nonyl-4-hydroxyquinoline-N-oxide; C025232:semiquinone radicals; C015286:funiculosin (anthraquinone); D014013:1,2-Dihydroxybenzene-3,5-Disulfonic Acid Disodium Salt; D000968:Antimycin A; D019802:Succinic Acid; D010088:Oxidoreductases; C022691:succinate oxidase