Effect of ischemic preconditioning on ischemia-reperfusion-injured myocardium and phosphorylated Akt during the disease course of diabetes in rats / 解放军医学杂志

ABSTRACT

Objective To evaluate the effect of ischemic preconditioning(IPC) on ischemia-reperfusion-injury of myocardium and phosphorylated Akt(p-Akt) during the disease course of diabetes in rats.Methods The rat model of diabetes mellitus was reprodused by streptozocin(40mg/kg,i.v.).Myocardial ischemia was then created by temporary ligation of a branch of the left anterior descending(LAD) coronary artery after 2 and 9 weeks,respectively.Thirty six SD rats were randomly divided into six groups(6 each)non-diabetic IPC(NDMIP) group,non-diabetic I/R(NDMIR) group,2-week diabetic IPC(2DMIP) group,2-week diabetic I/R(2DMIR) group,9-week diabetic IPC(9DMIP) group and 9-week diabetic I/R(9DMIR) group.Ischemic/reperfusion was induced by temporary occlusion of LAD coronary artery.After the experiment,creatine kinase-MB(CK-MB) isoenzyme and myocardial infarct size were measured,and the expression of p-Akt was detected by Western-blotting,the arrhythmia score was then evaluated.Results CK-MB level in NDMIP group was significantly lower than that in NDMIR group and 9DMIP group(P0.05);the arrhythmia score in 9DMIP group was significantly higher than that in 2DMIP group(P0.05);the expression of p-Akt in 9DMIP group was significantly lower than that in 2DMIP group(P0.05);the myocardial infarct size in 9DMIP group was larger than that in 2DMIP group.Conclusions IPC can provide significant microvascular protection against prolonged ischemia/reperfusion in acute diabetic rats,but not in chronic diabetic rats.The attenuation of myocardial protection by IPC may be associated with a decrease in p-Akt activation.