title: Distinct myoprotective roles of cardiac sarcolemmal and mitochondrial KATP channels during metabolic inhibition and recovery.
abstract: The protective roles of sarcolemmal (sarc) and mitochondrial (mito) KATP channels are unclear despite their apparent importance to ischemic preconditioning. We examined these roles by monitoring intracellular calcium ([Ca]int), using fura-2 and fluo-3, in enzymatically isolated rat right ventricular myocytes. Myocyte mortality, estimated using a trypan blue assay, changed approximately in parallel with changes in [Ca]int. Chemically induced hypoxia (CIH), induced by application of cyanide and 2-deoxy-glucose, caused a steady rise in [Ca]int. Calcium increased more rapidly on 'reoxygenation' by return to control solutions. The protein kinase C (PKC) activator PMA abolished both phases of calcium increase. The mitoKATP channel-selective blocker 5-hydroxydecanoate partially prevented the PMA-induced protection during CIH, but not during reoxygenation. In contrast, HMR 1098, a sarcKATP channel-selective blocker, abolished protection only during the reoxygenation. Adenosine (A1) receptor activation prevented or reduced increases in [Ca]int and improved cell viability via a PKC and mito/sarcKATP channel-dependent mechanism. PKC-dependent protection against cytoplasmic calcium increases was also observed in a human cell line (tsA201) transiently expressing sarcKATP channels. Protection was abolished only during the reoxygenation phase by the amino acid substitution (T180A) in the pore-forming Kir6.2 subunit, a mutation previously shown to prevent PKC-dependent modulation. Our data suggest that sarc and mitoKATP channel populations play distinct protective roles, triggered by PKC and/or adenosine, during chemically induced hypoxia/reoxygenation.
authors.affiliation: Department of Pharmacology, University of Alberta, Edmonton, Alberta, Canada. peter.light@ualberta.ca
authors.forename: P E
authors.initials: PE
authors.lastname: Light
authors.forename: H D
authors.initials: HD
authors.lastname: Kanji
authors.forename: J E
authors.initials: JE
authors.lastname: Fox
authors.forename: R J
authors.initials: RJ
authors.lastname: French
mesh_terms: D018528:ATP-Binding Cassette Transporters; D000241:Adenosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D001549:Benzamides / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D015687:Cell Hypoxia / Q000502:physiology; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D003652:Decanoic Acids / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects; D006352:Heart Ventricles / Q000166:cytology / Q000187:drug effects; D006801:Humans; D006880:Hydroxy Acids / Q000494:pharmacology; D019157:Ischemic Preconditioning, Myocardial; D054086:KATP Channels; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects; D008928:Mitochondria / Q000378:metabolism*; D009206:Myocardium / Q000378:metabolism; D010100:Oxygen / Q000494:pharmacology; D015221:Potassium Channels / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D024661:Potassium Channels, Inwardly Rectifying; D058906:Purinergic P1 Receptor Agonists; D058915:Purinergic P1 Receptor Antagonists; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000502:physiology; D012508:Sarcolemma / Q000378:metabolism*; D013997:Time Factors; D016276:Ventricular Function; D014970:Xanthines / Q000494:pharmacology
chemical_list: D018528:ATP-Binding Cassette Transporters; D001549:Benzamides; D003652:Decanoic Acids; D006880:Hydroxy Acids; D054086:KATP Channels; D008164:Luminescent Proteins; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D058906:Purinergic P1 Receptor Agonists; D058915:Purinergic P1 Receptor Antagonists; D011993:Recombinant Fusion Proteins; D014970:Xanthines; C092520:uK-ATP-1 potassium channel; C058394:2-chloro-N(6)cyclopentyladenosine; C052853:5-hydroxydecanoic acid; D000255:Adenosine Triphosphate; C051360:1,3-dipropyl-8-cyclopentylxanthine; C410297:HMR 1098; D000241:Adenosine; D010100:Oxygen; D002118:Calcium