title: [The effect of inhibitors of the Q-cycle on cyano-resistant oxidation of malate by rat liver mitochondria in the presence of menadione].
abstract: Based on the inhibitor analysis data, it has been assumed that the Q-cycle plays a role in the cyano-resistant malate oxidation induced by menadione (90 microM) in rat liver mitochondria. The extent of involvement of Q-cycle transmitters in the cyano-resistant respiration of mitochondria is determined by the mode of the electron supply into the Q-cycle. In the presence of dicumarol, i.e., under conditions when CoQ and menadione are reduced by NADH-quinone reductase, the bulk of the electrons pass through the o-center of the Q-cycle. Myxothiazole inhibits the respiration by 70-80%, while antimycin--by only 20-30%. In the presence of myxothiazole and antimycin menadione oxidizes cytochrome b. In the presence of rotenone, when menadione is reduced by DT-diaphorase, the rate of cyano-resistant respiration decreases approximately twofold; its sensitivity towards myxothiazole and antimycin drops down to 40%. In the absence of rotenone and dicumarol the Q-cycle does not participate in the cyano-resistant respiration which under these conditions is insensitive either to myxothiazole or to antimycin. It is concluded that the mechanism of cyano-resistant respiration changes with an alteration in the rates of quinones K3 and CoQ reduction. The mechanism of cyano-resistant respiration is also controlled by the medium tonicity. A reduction in the medium tonicity decrease the participation of the Q-cycle and, correspondingly, the sensitivity of the cyano-resistant respiration towards myxothiazole and antimycin.
authors.forename: G M
authors.initials: GM
authors.lastname: Kolesova
authors.forename: L V
authors.initials: LV
authors.lastname: Karnaukhova
authors.forename: N K
authors.initials: NK
authors.lastname: Segal'
authors.forename: L S
authors.initials: LS
authors.lastname: Iaguzhinskiĭ
mesh_terms: D000818:Animals; D000968:Antimycin A / Q000031:analogs & derivatives / Q000494:pharmacology; D003486:Cyanides / Q000494:pharmacology*; D004579:Electron Transport / Q000187:drug effects; D008293:Malates / Q000378:metabolism*; D008689:Methacrylates; D008930:Mitochondria, Liver / Q000187:drug effects / Q000378:metabolism*; D016660:NAD(P)H Dehydrogenase (Quinone) / Q000378:metabolism; D010084:Oxidation-Reduction; D051381:Rats; D012402:Rotenone / Q000494:pharmacology; D013844:Thiazoles / Q000494:pharmacology; D014451:Ubiquinone / Q000378:metabolism*; D014812:Vitamin K / Q000494:pharmacology*
chemical_list: D003486:Cyanides; D008293:Malates; D008689:Methacrylates; D013844:Thiazoles; D012402:Rotenone; C032456:antimycin; D014812:Vitamin K; D014451:Ubiquinone; D000968:Antimycin A; C030517:myxothiazol; C030298:malic acid; D016660:NAD(P)H Dehydrogenase (Quinone)
vernacular_title: Vliianie ingibitorov Q-tsikla na tsianrezistentnoe okislenie malata mitokhondriiami pecheni krys v prisutstvii menadiona.