短暂缺血阈强度运动促进心肌侧支循环生成的机制

目的 在小型猪可控性心肌缺血动物模型上,观察短暂缺血阈强度运动促进缺血区冠状动脉侧支循环生成的机制.方法 选择健康广西巴马小型猪32头,钝缘支装上水囊缩窄器制作可控性心肌缺血动物模型,4周后行冠状动脉造影证实模型建立成功.实验动物随机分为假手术组、单纯缺血组和运动组.单纯缺血组通过缩窄器注水加压制造心肌缺血,每日2次,每次2 min,每周5 d,共8周;运动组除制造静息状态心肌缺血外,每天还进行平板训练30 min,其中包括2次缺血阈强度运动,每次2 min,每周训练5 d,共8周.假手术组不作任何干预.采用微球测定训练前、后缺血区相对心肌血流量(RMBF);采用Western-blot及Real-time RT-PCR法测定缺血心肌局部血管内皮细胞生长因子(VEGF)及其受体胎肝激酶-1(Flk-1)的蛋白及mRNA表达量;采用ELISA法测定血清肌钙蛋白含量以确定训练的安全性;应用电镜观察心肌细胞损伤情况.结果 运动组RMBF显著高于单纯缺血组及假手术组(均P＜0.01);单纯缺血组RMBF亦显著高于假手术组(P＜0.01).运动组VEGF及Flk-1的蛋白及mRNA表达量均显著高于单纯缺血组及假手术组(P＜0.05,P＜0.01).单纯缺血组的VEGF及Flk-1的蛋白及mRNA表达量均显著高于假手术组(P＜0.05).单纯缺血组及运动组训练后,血清肌钙蛋白与训练前相比无显著增加(均P＞0.05).光镜及电镜检查无明显异常.结论 小型猪可控性心肌缺血动物模型给予适宜短暂缺血阈强度运动,可通过缺血心肌局部VEGF及其受体Flk-1的上调安全有效地促进冠状动脉侧支循环生成.

Intermittent exercise promotes collateral circulation in ischemic myocardial tissue

Objective To observe whether appropriate intermittent exercise at the ischemic threshold can safely promote collateral circulation in an ischemic area of the myocardium through the increased expression of vascular endothelial growth factor(VEGF)and its receptor fetal liver kinase-1(Fik-1). Methods A balloon constrictor was surgically implanted in the first obtuse marginal coronary artery(OM1)of miniature pigs.The subjects were divided into 3 groups:a sham-operation group,a pure ischemia group,and an exercise training group.Subjects in the exercise training group performed individualized treadmill programs 30 min daily,5 d per week,for 8 weeks,including 2 two-minute episodes of exercise-induced ischemia.Two pre-exercise episodes of pure ischemia induced by brief OM1 occlusion were also conducted.Only pure ischemia was induced in the pure ischemia group,and the sham-operation group remained sedentary for the experimental period.Relative myocardial blood flow(RMBF)was measured using microspheres.VEGF and Flk-1 expression levels were measured by Western blotting and real time RT-PCR analyses.Cardiac troponin I(ctnI)levels were determined using an enzyme-linked immunosorbent assay(ELISA). Light and electron microscopy were employed to examine myocardia damage in the ischemic area.Results RMBFs in the exercise training group were significantly higher than those in the pure ischemia and sham-operation groups. RMBFs in the pure ischemia group were significantly higher than those in the sham-operation group.The expression of VEGF and Flk-1 proteins and mRNAs in the exercise training group were significantly higher than those in the pure ischemia and sham-operation groups,and the levels in the pure ischemia group were also significantly higher than those in the sham-operation group.After training,no myocardial damage and no ctnI increase was observed in the pure ischemia group.Microscopy revealed no obvious structural changes. Conclusion Intermittent exercise at the isehemia threshold intension can safely promote coronary collateral formation through upregulation of VEGF and Flk-1 expression in the ischemic myocardial area of a porcine model.