RESUMO
Objective To investigate the protective effects of ischemic preconditioning on myocardial ischemia/reperfusion injury in diabetic rats.Methods Twenty-eight healthy male rats were injected streptozotocin at dose of 45 mg/kg by tail and be fed with normal diet for 4 weeks,then rats were randomly divided into iscbemia/reperfusion (I/R) group and ischemic preconditioning (IP) group.ST segment of electrocardiograph changes and arrhythmias of all rats were recorded before ischemia and 0,15,30 minuets after ischemia and 0.5,2 h after reperfusion.TTC staining was performed to determine myocardial infarct size.TUNEL assay was used to assesse cardiomyocyte apoptosis.The expression of antiapoptotic gene (Bcl-2) and proapoptotic (Bax) was determined by immunohistochemistry.Results Compared with I/R group,ST segment elevation of patients in IP group decrease from (0.675 ±0.150) mV to (0.489 ±0.161) mV at 30 min after ischemia(P ＜0.05).Meanwhile the onset of ventricular premature contraction(VPC) in IP group was (18.21 ± 5.36) min,later than that of control group ((6.47 ± 4.28) min,t =5.241,P =0.000).The duration of VPC was (6.07 ± 4.33) min,shorter than that of I/R group ((16.71 ± 5.48) min,t =4.924,P ＜ 0.01)).The incidence of ventricular tachycardia (VT) and ventricular fibrillation (VF) of lP group remarkably decreased compared with I/R group (VT:57.14％ (8/14) vs.14.29％ (2/14),x2 =5.600,P =0.018 ; VF:50.00％ (7/ 14) vs.14.29％ (2/14),x2 =4.094,P=0.043).The myocardial infarct size in IP group was (12.50 ± 9.45) ％,smaller than that of I/R group ((37.50 ± 11.40)％,t =3.211,P =0.006).Cardiomyocyte apoptotic index (AI) was attenuated in IP group than that of I/R group((24.31 ± 3.12)％ vs.(19.01 ± 4.32)％,t =3.227,P =0.006),which was correlate with increased the ratio of Bcl-2/Bax((0.103 ±0.045) vs.(0.221 ±0.101),t =2.670,P =0.015).Conclusion IP treatment for diabetic rats shows a protect effect on myocardial I/R injury through attenuating myocardial apoptosis,and increasing the ratio of Bcl-2/Bax.