The role of mitochondrial ATP sensitive potassium channel on cardioprotection of ischemic preconditioning and anesthetics

越来越多的证据提示，线粒体三磷酸腺苷敏感钾(mito-K&lt；ATP&gt；)通道在心肌缺血保护中可能起重要作用。在本研究中，我们观察了异丙酚、利多卡因和美西律对心肌细胞线粒体MITO-K通道活性的影响，以及MITO-K通道在缺血预适应(IPC)保护作用中的作用。在实验结束时，荧光变化归一化为暴露于5um 2，4-二硝基苯酚(DNP)后获得的黄素蛋白荧光。DNP是一种使呼吸与ATP合成分离并使线粒体电位崩溃的原生生物。二氮嗪(25um)是一种选择性mmito-K；ATP和gt；通道开放剂，可使线粒体可逆氧化至DNP值的63^+19%(n=7)。5-羟基癸酸(10…More 0uM)，一种选择性的mito-K&lt；ATP&gt；通道阻滞剂，可将二氮卓的氧化作用减弱到DNA值的2^+5%。异丙酚、利多卡因和美西律以浓度依赖的方式抑制二氮卓(100uM)诱导的黄素蛋白荧光。异丙酚、利多卡因和美西律的EC50分别为14.6ug/ml(n=9)、98±63uM(n=7)和107±42uM(n=7)。这些结果表明，异丙酚、利多卡因和美西律可减弱MITO-K通道的心肌保护作用。接下来，我们观察了MITO-K通道活动对IPC的影响。未预适应组(对照组)连续缺血15min，而预适应组(IPC组)先缺血5min，再灌注10min，最后再缺血15min。为了模拟缺血，我们使用了5um DNP。IPC组黄素蛋白荧光强度较对照组显著增强。这些结果表明，IPC的心脏保护作用是通过增加缺血刺激引起的心肌MITO-K、ATP和GT通道的活性来实现的。较少

Accumulating evidence suggets that mitochondrial adenosine triphoshate-senstive potassium (mito-K_<ATP>) channel may have an important role in the protection of myocardium during ischemia. In the present study, we examine the effects of propofol, lidocaine and mexiletine on mito-K_<ATP> channel activities and the role of mito-K_<ATP> channels on the carioprotective effects of ischemia-induced preconditioning (IPC) in isolated rat ventricular myocytes.Flavoprotein fluorescence was measured evaluate mitochondrial oxidation mediated by mito- K_<ATP> channels. The change of flourescence was normalized to baseline flavoprotein fluorescence obtained after exposure to 5uM 2, 4-dinitrophenol (DNP), a protonophore that uncouples respiration from ATP synthesis and collapses the mitochontrial potential, at the end of the experiments.Diazoxide (25uM), a selective mmito-K_<ATP> channel opener, caused reversible mitochondrial oxidation to 63 ^^+__- 19% of DNP values (n=7). 5-hydroxydecanoic acid (10 … More 0uM), a selective mito-K_<ATP> channel blocker, attenuated the oxidative effects of diazoxide to 2 ^+_- 5% of the DNA value. Propofol, lidocaine and Mexiletine inhibited diazoxide (100uM) -induced flavoprotein fluorescence in a concentration-dependent manner. The EC_<50> values of propofol, lidocaine and mexiletine were 14.6ug/ml (n=9) 98^^+__-63uM (n-7) and 107^^+__-42uM (n=7), respecitively. These results suggest that propofol, lidocaine and mexiletine may attenuate cardioprotective effects of mito-K__<ATP> channels.Next, we evaluated the effects of mito-K__<ATP> channel activities on IPC. Non-preconditioned group (control group) received a continuos 15 minutes ischemia, whereas preconditioned group (IPC group) subjected to 5 minutes ischemia, 10 minutes reperfusion, and finally 15 minutes ischemia. To simulate ischemia, we used 5uM DNP. Flavoprotein fluorescence of the IPC group was significantly increased compared to that of the control group. These results indicate that cardioprotective effects of IPC are due to increased activities of mito-K_<ATP> channels by ischemic stimulation. Less