CaMKⅡ与左西孟旦抗心肌缺血再灌注致大鼠心律失常作用的关系：离体实验

Relationship between CaMK Ⅱ and levosimendan against arrhythmia induced by myocardial ischemia- reperfusion in rats in vitro

目的评价心肌钙调素依赖性蛋白激酶Ⅱ（CaMKⅡ）与左西孟旦抗心肌缺血再灌注致大鼠心律失常作用的关系。方法健康成年雄性Wistar大鼠30只，体重250～300g，采用随机数字表法，将其分为3组（n=10）：对照组（C组）、缺血再灌注组（I／R组）和左西孟旦组（L组）。采用Langendorff灌注装置建立离体心脏灌注模型。平衡灌注20rain后，C组用K．H液继续灌注60min；I／R组缺血30min后，K-H液灌注30min；L组缺血30min后，用含左西孟旦300nmol／L的K-H液灌注30min。分别于缺血前即刻、再灌注15和30min时记录左心室发展压（LVDP）、左心室舒张末压（LVEDP）、左心室内压最大上升速率（＋dp／dtmax）、左心室内压最大下降速率（-dp／dtmax）和心率（HR）。记录再灌注期间心律失常的发生情况，并进行评分。于再灌注30min时取心尖部组织，测定细胞内钙离子浓度（[ca2＋]i），取左心室心肌组织，测定CaMKll的活性。结果与C组比较，I／R组心律失常评分、[Ca2＋]i和CaMKU活性升高，再灌注15和30min时LVDP、＋dp／dtmax、-dp／dtmax和HR降低，LVEDP升高（P〈0．05）；与I／R组比较，L组室性早搏数量、心律失常评分、[Ca2＋]i和CaMK11活性降低，再灌注15和30min时LVDP、＋dp／dtmax、-dp／dtmax和HR升高，LVEDP降低（P〈0．05）。结论左西孟旦降低心肌缺血再灌注致大鼠心律失常的机制与抑制CaMKlI活性有关。

Objective To evaluate the relationship between calmodulin protein kinase Ⅱ （CaMK Ⅱ ） and levosimendan against arrhythmias induced by myocardial ischemia-reperfusion （I/R） in rats in vitro. Methods Thirty male Wistar rats, weighing 250-300 g, were randomly divided into 3 groups （n = 10 each） using a random number table： control group （group C）, I/R group and levosimendan group （group L）. Their hearts were rapidly excised and perfused in a langendorff apparatus with K-H solution saturated with 95 % O2-5 % CO2 at 36.5-37.5 ℃ . At 20 min of equilibration, the hearts were perfused with K-H solution for 60 min in group C. The hearts were subjected to 30 min of ischemia followed by 30 min reperfusion with K-H solution in group I/R. The hearts were subjected to 30 min of isehemia followed by 30 min reperfusion with K-H solution containing 300 nmol/L levosimendan in group L. Left ventricle developed pressure （LVDP）, left ventricle end-diastolic pressure （LVEDP）, ＋ dP/dtmax, -dP/dtmax and heart rate （HR） were recorded immediately before ischemia and at 15 and 30 min of reperfusion. Arrhythmia was recorded during reperfusion and scored. Specimens were obtained from the apex of heart at 30 min of reperfusion for determination of the intracellular calcium concentration （ [ Ca2 ＋ ]1 i）. Myocardial specimens were obtained from the left ventricle at 30 min of reperfusion to detect CaMK Ⅱ activity. Results Compared with group C, arrhythmia score, [ Ca2＋] i and CaMK 11 activity were significantly increased, and LVDP, ＋dP/dtmax, -dP/dtmax and HR were decreased, and LVEDP was increased at 15 and 30 min of reperfusion in group I/R. Compared with group I/R, the number of ventricular premature beat, arrhythmia score, [Ca2＋ ] i and CaMK Ⅱ activity were significantly decreased, and LVDP, ＋ dP/dtmax, -dP/dtmax and HR were . increased, and LVEDP was decreased at 15 and 30 min of reperfusion in group L. Conclusion Inhibition of CaMK Ⅱ activity is involved in the mechanism by which levosimendan decreases the development of arrhythmias induced by myocardial I/R in rats.