Recombinant cardiac ATP-sensitive K+ channel subunits confer resistance to chemical hypoxia-reoxygenation injury.
BACKGROUND
Opening of cardiac ATP-sensitive K+ (KATP) channels has emerged as a promising but still controversial cardioprotective mechanism. Defining KATP channel function at the level of recombinant channel proteins is a necessary step toward further evaluation of the cardioprotective significance of this ion conductance.


RESULTS
KATP channel deficient COS-7 cells were found to be vulnerable to chemical hypoxia-reoxygenation injury that induced significant cytosolic Ca2+ loading (from 97+/-3 to 236+/-11 nmol/L). In these cells, the potassium channel opener pinacidil (10 micromol/L) did not prevent Ca2+ loading (from 96+/-3 nmol/L before to 233+/-12 nmol/L after reoxygenation) or evoked membrane current. Cotransfection with Kir6.2/SUR2A genes, which encode cardiac KATP channel subunits, resulted in a cellular phenotype that, in the presence of pinacidil (10 micromol/L), expressed K+ current and gained resistance to hypoxia-reoxygenation (Ca2+ concentration from 99+/-7 to 127+/-11 nmol/L; P>0.05). Both properties were abolished by the KATP channel blocker glyburide (1 micromol/L). In COS-7 cells transfected with individual channel subunits Kir6.2 or SUR2A, which alone do not form functional cardiac KATP channels, pinacidil did not protect against hypoxia-reoxygenation.


CONCLUSIONS
The fact that transfer of cardiac KATP channel subunits protected natively KATP channel deficient cells provides direct evidence that the cardiac KATP channel protein complex harbors intrinsic cytoprotective properties. These findings validate the concept that targeting cardiac KATP channels should be considered a valuable approach to protect the myocardium against injury.
Division of Cardiovascular Diseases, Department of Internal Medicine, Mayo Clinic and Mayo Foundation, Rochester, Minn, USA.
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Jovanović
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Jovanović
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Lorenz
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Terzic
D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D019556:COS Cells / Q000187:drug effects / Q000502:physiology; D002118:Calcium / Q000494:pharmacology; D002317:Cardiovascular Agents / Q000494:pharmacology; D015687:Cell Hypoxia / Q000502:physiology; D002478:Cells, Cultured / Q000187:drug effects; D006168:Guinea Pigs; D015428:Myocardial Reperfusion Injury / Q000503:physiopathology; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D018384:Oxidative Stress / Q000187:drug effects / Q000502:physiology; D020110:Pinacidil / Q000494:pharmacology; D015221:Potassium Channels / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D014162:Transfection / Q000502:physiology
D002317:Cardiovascular Agents; D015221:Potassium Channels; D011994:Recombinant Proteins; D020110:Pinacidil; D000255:Adenosine Triphosphate; D002118:Calcium