缺血预处理对幼兔心肌保护作用及其机制探讨

Myocardial protective effect of ischemic preconditioning and its mechanism in immature rabbit heart

目的 观察缺血预处理（ＩＰＣ）是否能保护接受全心离体缺血再灌注的未成熟兔心脏，并探讨ＡＴＰ敏感性钾通道在ＩＰＣ中的作用。方法 利用Ｌａｎｇｅｎｄｏｒｆ模型灌注幼兔（１４～２１ｄ）离体心脏，经历５ｍｉｎ缺血、１０ｍｉｎ再灌的ＩＰＣ后，用４℃的Ｓｔ．ＴｈｏｍａｓⅡ停搏液使心脏停跳，观察其在生理体温（３９℃）下接受４５ｍｉｎ缺血、４０ｍｉｎ再灌的血液动力学、冠脉流出液心肌酶及心肌能量变化。并利用ＡＴＰ敏感性钾通道阻断剂Ｇｌｉｂｅｎｃｌａｍｉｄｅ（Ｇｌｉ）作为工具药来研究ＩＰＣ保护作用的机制。结果ＩＰＣ明显改善心率（ＨＲ）、冠脉流出量（ＣＦ）、心脏功能指标（ＬＶＤＰ、±ｄｐ／ｄｔｍａｘ）恢复率，减少室性心律失常，保存心肌ＡＴＰ含量；肌酸磷酸激酶同工酶（ＣＫ－ＭＢ）漏出减少。预处理前灌注 Ｇｌｉ（１０μｍｏｌ／Ｌ）２０ｍｉｎ则完全消除了上述 ＩＰＣ的保护效应。结论 ＩＰＣ对经历全心缺血再灌注的未成熟兔心肌具有保护作用。这种保护效应可能涉及到ＡＴＰ敏感性钾通道的开放。

Objective To investigate whether ischemic preconditioning( IPC) could protect against ischemia-reperfusion injury in immature rabbit heart and the role of KATP channel in the mechanism of myocardial protection. Methods New Zealand rabbits aged 14-21 days weighing 220-280g were used. The animals were anesthetized and heparinized. Chest was opened and heart was quickly removed and aorta was connected to Langendorff preparation within 30 s. The hearts were perfused with Krebs-Henseleit buffer balanced with gas mixture(O2: CO2 = 95% : 5% ) at 60cmH2O2(perfusion pressure) . IPC consisted of 5 mm global ischimia plus 10 mm reperfusion. Glibenclamide was used as KATP channel blocker. Cardiac arrest was induced with cold(4℃ ) St Thomas Ⅱ cardioplegic solution and heart was made globally ischemic by withholding perfusion for 45 mm followed by 40 mm reperfusion. Thirty immature rabbit hearts were randomly divided into four groups: group Ⅰ( n= 9 control) was subjected to ischemia-reperfusion only; groupⅡ(n= 9 IPC + ischemia-reperfusion); group Ⅲ(n = 6 glibenclamide + ischemia-reperfusion) and group Ⅳ( n= 6 glibenclamide + IPC + ischemia-reperfusion) . Coronary flow(CF), HR, left ventricle developed pressure( LVDP) and ± dP/dt max were monitored before ischemia/IPC/glibenclamide( baseline value) and 5, 10, 20 and 40 mm after reperfusion and were expressed as percentage of their baseline values. Arrhythmia scores were recorded. Coronary effluent was collected at 10 miii after reperfusion was started for determination of CK-MB level. At the end of reperfusion 200mg myocardium was taken from apex for determination of ATP content. Results The group Ⅱ(IPC group) showed best results. The recovery of CF, HR, LVDP and ±dp/dt max, was best among the four groups. The incidence of arrhythmia was low and less CK-MB leaked out. Myocardial ATP content was better preserved. Pretreatment with glibenclamide completely abolished the myocardial protection provided by IPC but did not affect ischemiareperfusion injury. Conclusions IPC can protect against ischemia-reperfusion injury in immature rabbit bean. Activation of KATh channel is involved in the mechanism of myocardial protection of IPC.