title: Cardioselective sulfonylthiourea HMR 1098 blocks mitochondrial uncoupling induced by a KATP channel opener, P-1075, in beating rat hearts.
abstract: We investigated effects of blockade of cardiac ATP-sensitive potassium channels (KATP) with a novel cardioselective sulfonylthiourea, HMR 1098, on metabolic uncoupling caused by a potent KATP opener, P-1075, in Langendorff-perfused rat hearts. We used (1) 87Rb-NMR to detect activation-deactivation of sarcolemmal KATP, (2) 31P-NMR to monitor high-energy phosphates, (3) oxygen uptake measurements to monitor cellular respiration, and (4) myocardial optical absorbance measurements at 603 nm to follow changes in cytochrome c oxidase redox state. Activation of sarcolemmal KATP by P-1075 (5 microM) and a mitochondrial uncoupler 2,4-dinitrophenol (DNP) (50 microM) stimulated Rb+ efflux from the hearts by 130% and 60%, respectively. HMR 1098 (5 and 30 microM) blocked activation of sarcolemmal KATP in situ. HMR 1098 also prevented cardiac arrest and mitochondrial uncoupling induced by P-1075, such as (a) depletion of phosphocreatine and ATP by 40%, (b) two-fold decrease in venous oxygen, and (c) reduction of cytochrome c oxidase (demonstrated by an increase in 603 nm optical absorbance). The metabolic effects of P-1075 can be readily explained by activation of putative mitochondrial KATP. We concluded that blockade of mitochondrial uncoupling by HMR 1098 included an inhibiting effect of HMR 1098 on sarcolemmal and mitochondrial KATP in beating rat hearts.
authors.affiliation: Institute for Biodiagnostics, National Research Council, Manitoba, Winnipeg, Canada.
authors.forename: Olga
authors.initials: O
authors.lastname: Jilkina
authors.forename: Bozena
authors.initials: B
authors.lastname: Kuzio
authors.forename: Gary J
authors.initials: GJ
authors.lastname: Grover
authors.forename: Valery V
authors.initials: VV
authors.lastname: Kupriyanov
mesh_terms: D019297:2,4-Dinitrophenol / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001549:Benzamides / Q000494:pharmacology*; D003576:Electron Transport Complex IV / Q000187:drug effects / Q000378:metabolism; D006146:Guanidines / Q000494:pharmacology*; D007700:Kinetics; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism / Q000494:pharmacology*; D008929:Mitochondria, Heart / Q000187:drug effects / Q000378:metabolism*; D010085:Oxidative Phosphorylation / Q000187:drug effects; D010101:Oxygen Consumption / Q000187:drug effects; D010710:Phosphates / Q000378:metabolism; D010725:Phosphocreatine / Q000378:metabolism; D026902:Potassium Channel Blockers / Q000494:pharmacology*; D015221:Potassium Channels; D011725:Pyridines / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012508:Sarcolemma / Q000187:drug effects / Q000378:metabolism; D013453:Sulfonylurea Compounds / Q000494:pharmacology; D013890:Thiourea / Q000031:analogs & derivatives* / Q000494:pharmacology; D014475:Uncoupling Agents / Q000494:pharmacology
chemical_list: D001549:Benzamides; D006146:Guanidines; D008565:Membrane Proteins; D010710:Phosphates; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D011725:Pyridines; D013453:Sulfonylurea Compounds; D014475:Uncoupling Agents; C117780:mitochondrial K(ATP) channel; D010725:Phosphocreatine; C073896:N-cyano-N'-(1,1-dimethylpropyl)-N''-(3-pyridinyl)guanidine; D000255:Adenosine Triphosphate; C410297:HMR 1098; D003576:Electron Transport Complex IV; D013890:Thiourea; D019297:2,4-Dinitrophenol