title: Ca(2+)-induced mitochondrial membrane permeabilization: role of coenzyme Q redox state.
abstract: Rotenone-poisoned rat liver mitochondria energized by succinate addition, after a 5-min period of preincubation in presence of 10 microM Ca2+, produce H2O2 at much faster rates, undergo extensive swelling, and are not able to retain the membrane potential and accumulated Ca2+. Similar results were obtained when a suspension of rat liver mitochondria preincubated in anaerobic medium for 5 min was reoxygenated. The addition of either ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid, ruthenium red, catalase, or dithiothreitol, just before succinate or O2 addition, prevented mitochondrial swelling, indicating the involvement of Ca2+, reactive oxygen species, and oxidation of membrane protein thiols in this process of membrane permeabilization. Inhibition of mitochondrial swelling by cyclosporin A suggests that the membrane alterations observed under these experimental conditions are related to opening of the permeability transition pore. The presence of carbonyl cyanide p-trifluoromethoxyphenylhydrazone, which prevents Ca2+ cycling across the membrane, did not inhibit mitochondrial swelling when Ca2+ influx into the mitochondrial matrix was driven by a high Ca2+ gradient. When rotenone plus antimycin A-poisoned mitochondria were energized by N,N,N',N'-tetramethyl-p-phenylenediamine, which reduces respiratory chain complex IV, mitochondrial swelling did not occur, unless succinate, which reduces coenzyme Q, was also added. It is concluded that reduced coenzyme Q is the electron source for oxygen radical production during Ca(2+)-stimulated oxidative damage of mitochondria.
authors.affiliation: Departamento de Bioquímica, Universidade Estadual de Campinas, Brazil.
authors.forename: A J
authors.initials: AJ
authors.lastname: Kowaltowski
authors.forename: R F
authors.initials: RF
authors.lastname: Castilho
authors.forename: A E
authors.initials: AE
authors.lastname: Vercesi
mesh_terms: D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D006861:Hydrogen Peroxide / Q000378:metabolism; D008930:Mitochondria, Liver / Q000187:drug effects / Q000378:metabolism*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000494:pharmacology; D010539:Permeability / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D012402:Rotenone / Q000506:poisoning; D013386:Succinates / Q000494:pharmacology; D019802:Succinic Acid; D014451:Ubiquinone / Q000378:metabolism*
chemical_list: D013386:Succinates; D012402:Rotenone; D014451:Ubiquinone; D019802:Succinic Acid; D006861:Hydrogen Peroxide; D010100:Oxygen; D002118:Calcium