| Objective:1.To observe the effect of exercise on myocardial infarction area and Beclin 1 and atg-5 protein expression in isolated myocardial ischemia/reperfusion injury of aged rats.2.To investigate the protective effect of exercise preconditioning on myocardial ischemia/reperfusion injury in aged rats and its mechanism.Methods:Forty-eight aged male SD rats were randomly divided into control group,model group,exercise preconditioning + model group,exercise preconditioning + control group,twelve rats in each group.Langendorff perfusion system was adopted to establish a ischemia/reperfusion(I/R)model of isolated myocardial ischemia/reperfusion(I/R)in rats.Indicators detected in this experiment: all the indicators related to heart rate and cardiac function such as left ventricular development pressure were monitored and recorded at the end of balanced perfusion and reperfusion.After reperfusion,the myocardial infarction area was measured by TTC staining.The ultrastructure and autophagosome formation of old rat cardiac muscle cells were observed by transmission electron microscope.Western Blot was used to detect the protein expressions of Beclin 1and Atg5 in myocardium of aged rats.Results:1.Changes in cardiac function of rats in each group: compared with the model group,cardiac function indexes of the control group,the exercise + control group and the exercise + model group were all increased,with statistically significant differences(P <0.05).Compared with the control group,the cardiac function indexes in the exercise +control group were increased,and the difference was statistically significant(P < 0.05).2.Myocardial infarction area of rats in each group: compared with the model group,the area of myocardial infarction decreased in the exercise + model group,and the difference was statistically significant(P < 0.05).There was no myocardial infarction area in the control group and the exercise + control group.3.Changes in the ultrastructure and autophagosome of rat cardiac myocytes in eachgroup: the myocardial fibers in the control group and the exercise + control group were arranged neatly and closely under transmission electron microscope.The morphology of myocardial cells was normal and the nuclear membrane of cells was intact.In the model group,there were obvious autophagosomes,loose and disorderly arrangement of myocardial fiber bundles,swollen mitochondria of myocardial cells,and reduced cristae density,making it difficult to see complete organelle structure.The ultrastructure of myocardial cells in the exercise + model group was significantly improved compared with that in the model group.Under the electron microscope,it was observed that myofibrils were arranged neatly,sarcoplasmic integrity,mitochondrial morphology and structure were basically normal,and a small number of autophagosomes appeared in the field of vision.4.Beclin1 and atg-5 protein expression levels in rat myocardium of each group:compared with the model group,Beclin1 and atg-5 protein expression levels were significantly decreased in the control group,with statistically significant differences(P <0.01),and Beclin1 and atg-5 protein expression levels were decreased in the exercise +model group,with statistically significant differences(P < 0.05).Beclin 1 and atg-5 protein expressions in the myocardium of the control group were at the basic level.Compared with the control group,Beclin 1 and atg-5 proteins were increased in the exercise +control group,and the difference was statistically significant(P < 0.05).Conclusion:1.Exercise preconditioning can improve the cardiac function of aging rats,reduce the area of myocardial infarction,and play a protective role in the heart.2.Exercise preconditioning can reduce myocardial ischemia/reperfusion injury by regulating Beclin 1 and atg-5 protein expressions in myocardial cells of aging rats and reduce excessive autophagy of cardiomyocytes. |
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