Study of newly developed cardioplegia for long term myocardial preservation

心肌缺血再灌注损伤引起的钙超载被认为是心肌收缩力降低、自律性异常和心肌细胞死亡的主要原因。目前广泛应用的高钾去极化停搏液存在钙超载问题。在本研究中，我们进行了体外，体内和临床检查，以创建一个非去极化心脏停搏液。体外研究我们建立了用膜片钳技术测定大鼠心肌细胞膜电流的方法。本实验测定了离体大鼠心肌细胞Na/K泵电流，证实了甲磺酸萘莫司他对心肌细胞Na/K泵的抑制作用。体内研究AP 4A是P2 γ受体激动剂，具有ATP敏感性钾通道开放作用（1_<KATP>）。采用Langendorff离体大鼠心脏灌流法评价AP 4A的心肌保护作用。缺血前灌注AP 4A可明显改善缺血后的功能恢复。AP 4A的心肌保护作用与缺血预处理相似。这些结果表明，AP 4A是一种可能的非去极化心脏停搏液的成分。转染Na/Ca交换体表达基因可增强心肌对缺血再灌注损伤的耐受性。建立了HVJ-脂质体法基因转染的有效方法。用这种方法检测了诱导的HSP 70蛋白的保护作用。临床研究尼可地尔是临床使用的冠状动脉扩张剂之一，具有IKATP开放特性。在停搏液中加入尼可地尔可减轻去极化停搏液引起的钙超载。在冠状动脉旁路移植术病例中，心肺转流中添加尼可地尔的疗效的临床评价正在进行中。

Calcium overload induced by ischemia-reperfusion injury of the heart is regarded as a main cause of the reduction of contractility, abnormal automacitity and myocardial cell death. Hyper-kalemic depolarizing cardioplegia which is widely used has a disadvantage in the aspect of Ca overload. In this study, we performed in vitro, in vivo and clinical examination for creating a non-depolarizing cardioplegia. invitro study We established the method to measure membrane current of isolated rat cardiomyocytes, using the patch clamp method. We measured Na/K pump current of isolated rat cardiomyocyte and certificated the Na/K pump imhibition effects of Nafamostat mesilate. in vivo study AP4A is a P2y receptor agonist, and has an ability of openingv effect of ATP sensitive potassium channel (1_<KATP>). The myocardial protective effects of AP4A were evaluated using Langendorff perfusion of isolated rat heart. Preischemic infusion of AP4A significantly improved the post ischemic functional recovery. The myocardial protective effects of AP4A was similar to ischemic preconditioning. These results suggested that AP4A is a possible component of non-depolarizing cardioplegia. The transfection of Na/Ca exchanger expression gene can reinfore the myocardial tolerance against ischemia-reperfusion injury. We established the effective gene transfection method using HVJ-liposome method. Using this method, the protective effects of induced HSP 70 protein were examined. clinical study Nicorandil which is one of the clinical used coronary arterial dilator has IKATP opening properties. The addition of Nicorandil to cardioplegia may reduce Ca overload induced by depolarizing cardioplegia. The clinical evaluations of the efficacy of Nicorandil added to cardiopulmonary bypass in cases of coronary artery bypass grafting are now on going.