电针预治疗保护心肌缺血再灌注损伤——β-肾上腺素受体的耐受机制

目的:探讨电针预治疗对心肌缺血/再灌注性损伤的保护作用,以及心脏β-肾上腺素受体在其中扮演的角色。方法:采用结扎和再灌大鼠左冠状动脉前降支的方法建立实验性心肌缺血/再灌注(I/R)模型。40只雄性大鼠随机分为正常对照(NC)组、缺血再灌注(IR)组、缺血再灌注+电针(EA)组和缺血再灌注+电针+心得安(EAP)组。电针预处理方法是心肌缺血造模前连续3 d给予双侧“内关”穴电针,每次20 min,观察比较心肌缺血前反复电针预处理对心电图ST段、心肌缺血面积以及β1-肾上腺素受体蛋白表达的影响。结果:与NC组比较,IR组在缺血30 min及再灌注10 min后ST段明显抬高(均P<0.01);与IR组比较,EA组ST段抬高幅度明显降低(均P<0.01),而EAP组ST段抬高幅度与IR组相近,均明显高于EA组(P<0.01)。以梗塞区/危险区比值为指标的观察表明,IR组梗塞区/危险区比值明显高于NC组(P<0.01),而EA组该比值则明显低于IR组(P<0.01),EAP组该比值则与IR组相仿,明显高于EA组(P<0.01)。对β1-肾上腺素受体蛋白的观察表明,IR组该受体蛋白含量显著高于NC组(P<0.01),EA组与IR组相比,该蛋白含量则明显降低(P<0.01),而EAP组该蛋白含量却明显高于EA组(P<0.05),其值与IR组相近。结论:电针预治疗可以改善冠状动脉结扎引起的ST段抬高,减轻心肌缺血的程度,减少心肌梗塞面积,减低由于I/R导致β1-肾上腺素受体蛋白的过度表达,β-肾上腺素受体阻断剂心得安可以抑制其保护作用。可见,电针预治疗对心肌缺血具有保护作用,β-肾上腺素受体参与了介导针刺预处理改善上述心肌缺血性损害的作用。

Involvement of beta-adrenergic Receptor in the Protective Effect of Electroacupuncture Pretreatment on Myocardial Ischemia-reperfusion Injury in Rats

Objective: To observe the cardioprotective effects of repetitive pretreatment of electroacupuncture(EA) at higher intensity prior to the myocardial ischemia and reperfusion(MI/R) and to explore the involvement of beta-adrenergic receptor.Methods: Male SD rats were evenly randomized into normal control(NC),model,EA and EA propranolol groups.MI/R model was produced by occlusion of the anterior descending branch of the left coronary artery((30 min)) and reperfusion((10 min)) in the rats.ECG ST-segments and the ratio of infarct size/risk zone were detected,and the content of cardiac beta_1-adrenoceptor was assayed with immunoblot technique.EA((20 V),(20 Hz)) was applied to bilateral "Neiguan"(PC 6) for(30 min),once daily and continuously for 3 days.Propranolol((10 mg/kg),i.p) was given to the animals(15 min) before EA every time.Results: The elevated ST-segments of ECG in IR group recorded 30 min after ischemia and 10 min after reperfusion were significantly higher than those of NC group(P<0.01 and P<0.01 respectively);in EA group the elevated ST-segments were markedly reduced(P<0.01 and P<0.01 respectively vs IR group);while the elevated ST-segments in EAP group were almost the same as IR group,much higher than EA group(P<0.01 and P<0.01 respectively).The similar results were also achieved in the ratios of infarct size/risk zone in the 4 groups.Moreover,the content of cardiac beta_1-adrenoceptor(CCA) in EA group was significantly reduced as compared with IR group(P<0.01) in which CCA was significantly higher than NC group(P<0.01).In EAP group the CCA was almost the same as that in IR group(P>0.05) and much higher than EA group(P<0.05).Conclusion: The results of the present study indicate that by mimicking the ischemic preconditioning,pretreatment of EA can protect the heart from injury of MI/R in rats.The protective effect of EA is mediated by cardiac beta_1-adrenoceptor.