Opening of mitochondrial K(ATP) channels attenuates the ouabain-induced calcium overload in mitochondria.
We tested whether opening of mitochondrial ATP-sensitive K(+) (mitoK(ATP)) channels depolarizes mitochondrial membrane potential (DeltaPsi(m)) and thereby prevents the mitochondrial Ca(2+) overload. With the use of a Nipkow disk confocal system, the mitochondrial Ca(2+) concentration ([Ca(2+)](m)) and DeltaPsi(m) in rat ventricular myocytes were measured by loading cells with Rhod-2 and JC-1, respectively. Exposure to ouabain (1 mmol/L) for 30 minutes produced mitochondrial Ca(2+) overload, and the intensity of Rhod-2 fluorescence significantly increased to 173+/-16% of baseline (P<0.001). Treatment of myocytes with the mitoK(ATP) channel opener diazoxide (100 micromol/L) blunted the ouabain-induced mitochondrial Ca(2+) overload (131+/-10% of baseline; P<0.001 versus ouabain). Moreover, diazoxide significantly depolarized the DeltaPsi(m) and reduced the intensity of JC-1 fluorescence during application of ouabain to 89+/-2% of baseline (P<0.05). These effects of diazoxide were blocked by the mitoK(ATP) channel blocker 5-hydroxydecanoate (500 micromol/L). These results indicate that opening of mitoK(ATP) channels prevents a mitochondrial Ca(2+) overload in association with DeltaPsi(m) depolarization and thereby protects myocardium against ischemic damage.
Ishida
H
H
Department of Physiology, Tokai University School of Medicine, Isehara, Japan.
Hirota
Y
Y
Genka
C
C
Nakazawa
H
H
Nakaya
H
H
Sato
T
T
D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D003652:Decanoic Acids / Q000494:pharmacology; D003981:Diazoxide / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005456:Fluorescent Dyes; D006352:Heart Ventricles / Q000166:cytology / Q000378:metabolism; D006880:Hydroxy Acids / Q000494:pharmacology; D008565:Membrane Proteins / Q000187:drug effects / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D018715:Microscopy, Video; D008929:Mitochondria, Heart / Q000187:drug effects / Q000378:metabolism*; D009206:Myocardium / Q000166:cytology / Q000378:metabolism; D010042:Ouabain / Q000494:pharmacology*; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism; D051381:Rats
D003652:Decanoic Acids; D004791:Enzyme Inhibitors; D005456:Fluorescent Dyes; D006880:Hydroxy Acids; D008565:Membrane Proteins; D015221:Potassium Channels; C117780:mitochondrial K(ATP) channel; D010042:Ouabain; C052853:5-hydroxydecanoic acid; D000255:Adenosine Triphosphate; D003981:Diazoxide; D002118:Calcium