Mitochondrial Ca2+-activated K+ channels more efficiently reduce mitochondrial Ca2+ overload in rat ventricular myocytes.
We investigated the role of the mitochondrial ATP-sensitive K(+) (K(ATP)) channel, the mitochondrial big-conductance Ca(2+)-activated K(+) (BK(Ca)) channel, and the mitochondrial permeability transition pore (MPTP) in the ouabain-induced increase of mitochondrial Ca(2+) in native rat ventricular myocytes by loading cells with rhod 2-AM. To overload mitochondrial Ca(2+), we pretreated cells with ouabain before applying mitochondrial K(ATP) or BK(Ca) channel and/or MPTP opener. Ouabain (1 mM) increased the rhod 2-sensitive fluorescence intensity (160 +/- 5.0% of control), which was dramatically decreased to the control level on application of diazoxide and NS-1619 in a dose-dependent manner (half-inhibition concentrations of 78.3 and 7.78 muM for diazoxide and NS-1619, respectively). This effect was reversed by selective inhibition of the mitochondrial K(ATP) channel by 5-hydroxydecanoate, the mitochondrial BK(Ca) channel by paxilline, and the MPTP by cyclosporin A. Although diazoxide did not efficiently reduce mitochondrial Ca(2+) during prolonged exposure to ouabain, NS-1619 reduced mitochondrial Ca(2+). These results suggest that although mitochondrial BK(Ca) and K(ATP) channels contribute to reduction of ouabain-induced mitochondrial Ca(2+) overload, activation of the mitochondrial BK(Ca) channel more efficiently reduces ouabain-induced mitochondrial Ca(2+) overload in our experimental model.
Kang
Sung Hyun
SH
Mitochondrial Signaling Laboratory, Department of Physiology and Biophysics, College of Medicine, Biohealth Products Research Center, Inje University, 633-165 Gaegeum-Dong, Busanjin-Gu, Busan 613-735, Korea.
Park
Won Sun
WS
Kim
Nari
N
Youm
Jae Boum
JB
Warda
Mohamad
M
Ko
Jae-Hong
JH
Ko
Eun A
EA
Han
Jin
J
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D006352:Heart Ventricles / Q000166:cytology / Q000378:metabolism*; D015640:Ion Channel Gating / Q000502:physiology*; D008928:Mitochondria / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000378:metabolism*; D032383:Myocytes, Cardiac / Q000378:metabolism*; D024681:Potassium Channels, Calcium-Activated / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley
D024101:Mitochondrial Proteins; D024681:Potassium Channels, Calcium-Activated; D002118:Calcium