心肌缺血周负荷对兔心肌血管内皮生长因子表达的影响

The effects of weekly myocardial ischemic burden on expression of VEGF in myocardium of rabbitsGU

目的:研究不同心肌缺血周负荷对兔心肌血管内皮生长因子(VEGF)表达的影响。方法:健康成年新西兰兔35只,体重2.2—2.5kg。根据不同的周缺血天数随机分为对照组、假手术组、3天/周组、5天/周组和7天/周组。将气囊梗阻器安装在冠状动脉左室支处,建立可控性心肌缺血模型。日缺血负荷为2min/h,2次/天,持续缺血刺激4周。取缺血区心肌观察形态学改变,并采用Western Blot方法检测缺血区和非缺血区心肌VEGF的表达水平。结果:①气囊充气后可以安全、有效地诱发心肌缺血。②与对照组和假手术组相比,缺血组左室支支配区心肌VEGF表达显著增高(P<0.05);各缺血亚组间VEGF表达差异无显著性意义(P>0.05)。③假手术组心肌VEGF表达与对照组相比无明显变化(P>0.05)。④左室支支配区心肌VEGF表达和冠状动脉侧支血流量(CCBF)呈正相关(r=0.775,P<0.01)。结论:持续4周间断性心肌缺血可显著提高缺血区心肌VEGF表达,不同周缺血负荷对其表达无明显影响;缺血区心肌VEGF表达水平和CCBF相关。

Objective：To investigate the effects of weekly myocardial ischemic burden on expression of vascular endothelial growth factor （VEGF） in hearts of rabbits.Method：Thirty-five adult New Zealand rabbits （2.2-2.5kg） were randomly divided into the control group, sham-operated group and ischemic groups which were subdivided into 3,5 and 7-days subgroups in terms of the weekly frequencies of ischemic stimulation.Controlled myocardial ischemia model was established by installing a balloon occluder on the left ventricular branch （LVB）.Upon a seven-day postoperative recovery, 2-min occlusions per hour on LVB with different weekly ischemic burdens by inflating the balloon occluder were performed twice a day and lasted for 4 weeks, meanwhile ECG was observed. The ischemic myocardium was sampled for histological examination. The expression levels of VEGF in ischemic and non-ischemic myocardium were quantified by Western Blot.Result： （1）The inflation of the balloon occluder momentarily induced elevation of ST segment, which indicated safe and effective onset of myocardial ischemia. （2）Compared with control and sham-operated group, the expression of VEGF obviously increased in the ischemic groups （P〈0.05） while no significant differences among these subgroups were observed（P〉0.05）.（3）VEGF levels remained similar in myocardium of both control and sham-operated groups（P〉0.05）.（4）VEGF levels in ischemic myocardium were positively correlated with coronary collateral blood flow （r=0.775,P〈0.01）.Conelusion：Intermittent myocardial ischemia for four weeks may increase the expression of VEGF in ischemic myocardium while increment of weekly ischemic burden does not enhance expression of VEGF further. There is a certain correlation with regard to VEGF levels of ischemic myocardium and coronary collateral blood flow.