Distinct myoprotective roles of cardiac sarcolemmal and mitochondrial KATP channels during metabolic inhibition and recovery.
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.
Light
P E
PE
Department of Pharmacology, University of Alberta, Edmonton, Alberta, Canada. peter.light@ualberta.ca
Kanji
H D
HD
Fox
J E
JE
French
R J
RJ
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
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