Abstract: Objective: To investigate the changes of ultrastructure of myocardial cells and the expression levels of tumor necrosis factor α(TNF-α) in myocardium tissue of the diabetic rabbits during early myocardial ischemia and their mechanisms,and to provide the theoretical basis for studying the pathogenesis of diabetic myocardial ischemia injury. Methods: A total of 42 healthy male New Zealand white rabbits were chosen.The method of intravenous injection of alloxan in ear vein was used to establish the diabetic models in 26 rabbits among 42 rabbits; the method of partial ligation of left anterior descending coronary artery by thoracotomy was used to establish the diabetic myocardial ischemia models in 22 model rabbits with diabetes.Atotal of 16 (modeling succesfully) were divided into diabetic myocardial ischemia 7 d group and 28 d group;other 16 rabbits were used as sham operation groups at the relevant time points(7 and 28 d),and there were 8 rabbits in each group.The ultrastructure of myocardial cells was observed by transmission electron microscope; the apoptosis index (AI) of myocardial cells in ischemic myocardium tissue of the rabbits was detected by TUNEL method; the expression levels of TNF-α in ischemic myocardium tissue of the rabbits were detected by real-time RT-PCR method. Results: In sham operation groups,the nuclei of myocardial cells was bigger,the nuclear chromatin was in uniform distribution,the myofibril ordered arrangement,the sarcomere was neat;the mitochondria between myofibril were rich,and their structures were clear.For the rabbits in diabetic myocardial ischemia group,their early-stage cardiocyte nuclei were irregular in shape,myofibrils was loose in structure,the part of myofibril was broken,and the mitochondrial hyperplasia between the myocardial cells was obvious.Compared with sham operation groups,the AI of myocardial cells and the expression levels of TNF-α in the ischemic myocardial cells of the rabbits in diabetic myocardial ischemia 7 d and 28 d groups were significantly increased(P<0.05),and the indexes mentioned above in diabetic myocardial ischemia 7 d group was higher than those in diabetic myocardial ischemia 28 d group(P<0.05). Conclusion: The destruction of ultrasturctue and obvious apoptosis of the myocardial cells of the rabbits occur in the early stage of diabetic myocardial ischemia.The increasing of expression level of TNF-α may involve in the myocardial ischemic injury.

Key words: apoptosis, myocardial ischemia, tumor necrosis factor-α, diabetes mellitus