线粒体钙激活及ATP敏感钾通道在肢体远距预处理心肌保护中的作用

目的 研究心肌细胞线粒体钙激活钾通道（MitoKCa）与线粒体ATP敏感钾通道(MitoKATP)在肢体远距预处理（RPC）心肌保护中的作用。方法 雄性SD大鼠72只，分为9组：单纯缺血复灌（I/R）组、RPC组、MitoKATP 开放剂（DZ）组、MitoKCa 开放剂NS1619组、MitoKCa 开放阻断剂RPC+paxilline组、MitoKATP 开放阻断剂RPC+5-HD (5 hydroxydeconate)组、RPC+NS1619+5 HD组、RPC+paxilline+DZ组和RPC+paxilline+5 HD组，每组8只。RPC模型用结扎大鼠股动脉5min，松开复灌5min，共4个循环的方法制备。各组I/R模型通过结扎离体心脏冠状动脉前降支30min，松开复灌120min进行制备。检测各组心脏血流动力学变化，TTC染色法测量心肌梗死面积，可见分光光度法检测冠脉流出液中LDH含量。结果 与I/R组相比，NS1619（10μmol/L）和DZ（50μmol/L）作用与远距预处理RPC组相似，改善复灌后心功能，减小心肌梗死面积，抑制了LDH释放(P<0.01)，但与 RPC组相比差异无统计学意义（P>0.05）。给予Paxilline（1μmol/L）或 5-HD (100μmol/L），取消了RPC的心肌保护作用 (P<0.01)。阻断MitoKCa和MitoKATP中的一种通道，开放另一种通道仍可起到心肌保护作用，且与RPC组无明显差异(P＞0.05);同时给与两种通道的阻断剂，发现与单独阻断一种通道相比，心肌细胞损伤程度加大 (P<0.01)。 结论 心肌细胞线粒体钙激活钾通道MitoKCa和线粒体ATP敏感钾通道MitoKATP开放都参与了RPC的心肌保护作用，两者发挥作用的方式可能是相互独立的，但作用结果具有协同性。

Roles of mitochondrial calcium-activated potassium channel and ATP-sensitive potassium channel in myocardial protection by limb remote preconditioning

Objective To investigate the roles of mitochondrial calcium-activated potassium channel (MitoKCa) and mitochondrial ATP-sensitive potassium channel (MitoKATP) in myocardial protection by limb remote preconditioning (RPC). Methods Seventy-two Male Sprague Dawley rats were divided into nine groups( eight per group): ischemia reperfusion group（I/R）, RPC group, MitoKATP-channel opener group （diazoxide, DZ）, MitoKCa-channel opener group （NS1619）, MitoKCa inhibitor group （RPC+paxilline）, MitoKATP inhibitor group（RPC+5-HD）, RPC+NS1619+5-HD group, RPC+paxilline+DZ group and RPC+paxilline+5-HD group. Preparation of RPC model was made by the ligation of rat femoral artery for 5min followed by 5min reperfusion. The procedures was repeated for 4 times; Preparation of I/R model was made by the ligation of anterior descending coronary artery for 30min followed by 120min reperfusion. Heart hemodynamics of each group was measured. Size of myocardium infarction was measured by TTC staining method and the content of LDH in the effusion from coronary artery was detected spectrophotometrically. Results Compared to I/R group, administration of NS1619(10μmol/L) and DZ(50μmol/L) both improved heart function, decreased myocardium infarction and restrained the release of LDH (P<0.01), which were similar to the remote ischemic preconditioning(RPC) group (P>0.05). However, no difference was observed when compared with RPC group (P>0.05). Administration of paxilline (1μmol/L) or 5 HD (100μmol/L) abolished the protective effect of RPC (P<0.01). When one of the two (MitoKCa and MitoKATP) channels was blocked while the other was activated, cardiac protection was still observed. And there was no significant difference when compared to RPC group (P>0.05). When both channels was inhibited by the corresponding inhibitors at the same time, aggravated heart injury was noted compared to the situations in which only one of the two was blocked (P<0.01). Conclusion Opening of both MitoKCa and MitoKATP channels participates in the myocardial protection in limb remote ischemic preconditioning. They may work in independent but cooperative ways.