Elucidation of molecular biological mechanism of Ischemic preconditioning-northern blot analysis of m-RNA in ATP sensitive potassium channel

用单个或多个短暂的缺血和再灌注期预处理心脏使心脏对随后的缺血性损伤具有很强的抵抗力。心肌预适应现象现已在动物中得到证实，也可能存在于人体中。然而，还没有研究证实缺血预适应的分子生物学机制。ATP敏感性钾通道是缺血预适应的机制之一。然而，目前还没有报道证实缺血预适应的分子生物学机制。有两个亚基被报道为ATP敏感的K+通道。一个是大鼠SUR-2，另一个是小鼠kir 6.2。材料与方法将大鼠心脏缺血预处理分为6组：1组为未预处理对照组，2组为缺血2.5min再灌注15 min组，3组为缺血2.5min再灌注15 min组，4组为缺血5 min再灌注15 min组，5组为缺血2.5min再灌注15 min组，6组为缺血2.5min再灌注15 min组，7组为缺血2.5min再灌注15 min组，8组为缺血2.5min再灌注15 min组。第5组为第4组的2个周期，第6组为缺血10 min后再灌注15 min。北方印迹分析进行预处理左心室muscle在each group.Results和CommentsIn本研究中，SUR-2 m-RNA是缺乏在离体缺血预处理大鼠心脏。提示缺血预适应可能不是由ATP敏感性K+通道介导的，但ATP敏感性K+通道可能是由至少两个亚基组成的复合体，大鼠的SUR-s和小鼠的kir6.2两个亚基都不能单独产生K+通道活性，因此，需要利用两个亚基组成的复合体进行进一步的研究。大鼠SUR-2和小鼠kir 6.2证实缺血预适应不是由ATP敏感性K+通道介导的。

Preconditioning the heart with single of multiple brief periods of ischemia and reperfusion makes the heart very resistant to a subsequent ischemic insult. The phenomenon of myocardial preconditioning has now been confirmed in animals and may also exist in humans. However, no study has confirmed the molecular biological mechanism of ischemic preconditioning. ATP-sensitive K+ channel has been reported to be one of the mechanisms of ischemic preconditioning. However, there is no report that has verified molecular biological mechanisms of ischemic preconditioning. Two subunits have reported as ATP-sensitive K+ channels. One is rat SUR-2 and another is mouse kir 6.2. In the present study, we investigated whether ischemic preconditioning is mediated by SUR-2 using northern blot analysis.Materials and MethodsIschemic preconditioned rat hearts were divided to following six groups : group 1, no preconditioned control; group2, 15 min of reperfusion following 2.5 min of ischemia ; group3, 2 cycles of group2 ; group4, 15 min of reperfusion follwing 5 min of ischemia ; group5, 2 cycles of group4 ; group6, 15min of sreperfusion following 10 min of ischemia. Northern blot analysis were performed using predconditioned left ventricular muscle in each group.Results and CommentsIn the present study, SUR-2m-RNA was absent in isolated ischemic preconditioned rat hearts. The present results indicate that ischemic preconditioning may not be mediated by ATP-sensitive K+ channels, However, ATP-sensitive K+ channels may be a complex composed of at least two subunits, rat SUR-s and mouse kir 6.2 Neither subunit alone can produce K+ channel activity, and the therefore, further study should be conducted by using a complex composed of two subunits, rat SUR-2 and mouse kir 6.2 to confirm that ischemic preconditioning is not mediated by ATP-sensitive K+ channels.