title: 4,6-Dinitro-o-cresol uncouples oxidative phosphorylation and induces membrane permeability transition in rat liver mitochondria.
abstract: The effect of the herbicide 4,6-dinitro-o-cresol (DNOC), a structural analogue of the classical protonophore 2,4-dinitrophenol, on the bioenergetics and inner membrane permeability of isolated rat liver mitochondria was studied. We observed that DNOC (10-50 microM) acts as a classical uncoupler of oxidative phosphorylation in rat liver mitochondria, promoting both an increase in succinate-supported mitochondrial respiration in the presence or absence of ADP and a decrease in transmembrane potential. The protonophoric activity of DNOC was evidenced by the induction of mitochondrial swelling in hyposmotic K(+)-acetate medium, in the presence of valinomycin. At higher concentrations (> 50 microM), DNOC also induces an inhibition of succinate-supported respiration, and a decrease in the activity of the succinate dehydrogenase can be observed. The addition of uncoupling concentrations of DNOC to Ca(2+)-loaded mitochondria treated with Ruthenium Red results in non-specific membrane permeabilization, as evidenced by mitochondrial swelling in isosmotic sucrose medium. Cyclosporin A, which inhibits mitochondrial permeability transition, prevented DNOC-induced mitochondrial swelling in the presence of Ca2+, which was accompanied by a decrease in mitochondrial membrane protein thiol content, owing to protein thiol oxidation. Catalase partially inhibits mitochondrial swelling and protein thiol oxidation, indicating the participation of mitochondrial-generated reactive oxygen species in this process. It is concluded that DNOC is a potent potent protonophore acting as a classical uncoupler of oxidative phosphorylation in rat liver mitochondria by dissipating the proton electrochemical gradient. Treatment of Ca(2+)-loaded mitochondria with uncoupling concentrations of DNOC results in mitochondrial permeability transition, associated with membrane protein thiol oxidation by reactive oxygen species.
authors.affiliation: Departamento de Patologia Clínica NMCE, Faculdade de Ciĕncias Médicas, Universidade, Estadual de Campinas, SP, Brazil.
authors.forename: R F
authors.initials: RF
authors.lastname: Castilho
authors.forename: J A
authors.initials: JA
authors.lastname: Vicente
authors.forename: A J
authors.initials: AJ
authors.lastname: Kowaltowski
authors.forename: A E
authors.initials: AE
authors.lastname: Vercesi
mesh_terms: D019297:2,4-Dinitrophenol / Q000494:pharmacology; D000818:Animals; D004138:Dinitrocresols / Q000494:pharmacology*; D008930:Mitochondria, Liver / Q000187:drug effects*; D010085:Oxidative Phosphorylation / Q000187:drug effects*; D010101:Oxygen Consumption; D010316:Particle Size; D010539:Permeability / Q000187:drug effects; D018892:Proton-Motive Force; D051381:Rats; D017208:Rats, Wistar; D014475:Uncoupling Agents / Q000494:pharmacology*
chemical_list: D004138:Dinitrocresols; D014475:Uncoupling Agents; C024132:4,6-dinitro-o-cresol; D019297:2,4-Dinitrophenol