| Objective:The effect of exercise preconditioning on myocardial infarction area and the expression of Beclin 1 and LC3-Ⅱ protein after myocardial ischemia/reperfusion injury in rats was studied,and the mechanism of myocardial protection was discussed.Methods:54 male SD rats were randomly divided into sham operation group,model group and exercise preconditioning group,with 18 rats in each group.A rat model of myocardial ischemia/reperfusion(I/R)was made by ligation of the left anterior descending branch of the coronary artery(LAD).After myocardial ischemia 30 min,loosened the ligature line and restored blood flow to achieve reperfusion.The whole ECG,reperfusion after 1h,EB-TTC double staining method was used to determine infarct size in rats;the ultrastructure of myocardial cells and the formation of autophagy in rats were observed by transmission electron microscopy;the apoptosis of myocardial cells was observed in TUNEL;staining the expression of Beclin 1 and LC3-Ⅱprotein was detected by Western Blot.Results:1.Myocardial infarction area of rats in each group:there was no myocardial ischemia and infarction in the sham operation group,there was no significant difference in the range of ischemic area between the other groups(P>0.05);compared with the model group,the IS and IS/AAR of the exercise preconditioning group decreased significantly,the difference was statistically significant(P<0.05).2.Ultrastructure of myocardial cells and formation of autophagy in rats of each group:under transmission electron microscope,the myocardial cells in the sham operation group were observed to be normal,the surrounding space of the nucleus was visible,the cell nuclear membrane was complete and continuous,the structure of mitochondria was intact,there was no edema,the muscle fiber bundles were arranged in order,a few muscle fibers were edema,and the autophagic corpuscle was not found;Severe injury,disorder and interruption of ridge arrangement,it is difficult to see complete organelles,myofibrils looseness disorder,interstitial edema,and autophagosum formation in the field of vision;the myocardial cell injury of the exercise preconditioning group is lighter,mitochondria structure is more complete,slight edema,partial sarcoplasmic reticulum edema,dilatation,autophagosum is less.3.Apoptosis of rat cardiac myocytes in each group:the sham operation group rats only a handful of TUNEL positive cells;compared with the sham operation group,the ratio of TUNEL positive cells in the model group increased significantly,and the difference was statistically significant(P<0.05);compared with the model group,the ratio of TUNEL positive cells in the exercise preconditioning group was significantly lower than that in the model group(P<0.05).4.Beclin 1 and LC3-Ⅱ protein expression were found in each group:the expression of Beclin 1 and LC3-Ⅱ protein in rat myocardium,Beclin 1 and LC3-Ⅱ protein expression in sham operation group.Compared with sham operation group,the level of Beclin 1 and LC3-Ⅱ was up,the difference was statistically significant(P<0.05).Compared with the model group,the Beclin 1 and LC3-Ⅱ protein levels in the exercise preconditioning group were significantly lower than those in the model group(P<0.05).Conclusions:1.Exercise preconditioning can induce myocardial ischemia tolerance,inhibit myocardial apoptosis and reduce infarct size,alleviate myocardial ischemia/reperfusion injury.2.Exercise preconditioning can reduce the expression of Beclin 1 and LC3-II protein,induce moderate autophagy,and improve the structure of myocardial ischemia reperfusion myocardium. |
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