Ishida H, Hirota Y, Genka C, Nakazawa H, Nakaya H, Sato T
Department of Physiology, Tokai University School of Medicine, Isehara, Japan.
Circ Res. 2001 Nov 9;89(10):856-8. doi: 10.1161/hh2201.100341.
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+)) 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.
我们检测了线粒体ATP敏感性钾通道（mitoK(ATP)）开放是否会使线粒体膜电位（ΔΨm）去极化，从而防止线粒体钙超载。利用尼普科夫圆盘共聚焦系统，分别通过用Rhod-2和JC-1装载细胞来测量大鼠心室肌细胞中的线粒体钙浓度（[Ca2+]m）和ΔΨm。用哇巴因（1 mmol/L）处理30分钟会导致线粒体钙超载，Rhod-2荧光强度显著增加至基线的173±16%（P<0.001）。用mitoK(ATP)通道开放剂二氮嗪（100 μmol/L）处理心肌细胞可减轻哇巴因诱导的线粒体钙超载（为基线的131±10%；与哇巴因相比，P<0.001）。此外，在应用哇巴因期间，二氮嗪使ΔΨm显著去极化，并将JC-1荧光强度降低至基线的89±2%（P<0.05）。二氮嗪的这些作用被mitoK(ATP)通道阻滞剂5-羟基癸酸（500 μmol/L）阻断。这些结果表明，mitoK(ATP)通道开放可防止与ΔΨm去极化相关的线粒体钙超载，从而保护心肌免受缺血损伤。
