Study On The Protection Of Noninvasive Delayed Limb Ischemic Preconditioning Against Myocardial Ischemia-reperfusion Oxidative Injury In Diabetic Rats

Objective:To study the protection of noninvasive delayed limb ischemic preconditioning(NDLIP) against myocardial ischemia/reperfusion oxidative injury in diabetic rats.Methods:Diabetic rat models were induced by injection of streptozotocin(STZ) into the vena caudalis.The diabetic rats were divided randomly into three groups. (1)myocardial ischemia/reperfusion(I/R) group:rats were subjected to 30 min occlusion and 120 min reperfusion of the left anterior descending(LAD) coronary artery;(2)early myocardial ischemic preconditioning(EMIP) group:rats were subjected to three episodes of 5 min of ischemia coupled to 5 min of reperfusion in the LAD before 30 min occlusion and 120 min reperfusion of LAD;(3)NDLIP group:rats were pretreated with three cycles of five minutes ischemia/five minutes reperfusion on the left hind limb,once a day for three consecutive days,to establish the NDLIP models.On the forth day,30 min occlusion and 120 min reperfusion of LAD was performed.The electrocardiogram was monitored continuously to record ventricular arrhythmia(VA) during 30 min ischemia.Cardiac troponin I(cTnI) content was determined using enzyme linked immunosorbent assay (ELISA).I/R-induced infarct size was determined using 2,3,5-triphenyltetrazolium chloride(TTC) staining.Myocardial total superoxide dismutase(T-SOD) and manganese superoxide dismutase (Mn-SOD) activity,and malondialdehyde(MDA) content were detected by spectrophotometer.Mn-SOD mRNA expression in cardiomyocytes was measured by reverse transcription polymerase chain reaction(RT-PCR).Results:1.Influnce of NDLIP on the physiologic changes after I/RCompared with I/R group,EMIP and NDLIP could delay the onset of ventricular premature contraction(VPC)(6.21±2.12 min vs 12.29±4.93 min and 10.63±2.99 min,respectively,P＜0.01),shorten the duration of VPC(15.34±4.91 min vs 8.28±2.31 min and 6.81±2.75 min,respectively,P＜0.01), decrease incidences of ventricular tachycardia(VT) and ventricular fibrillation(VF),and lower the raise degree of ST-segment.There was no significance on heart rate(HR) and mean arterial blood pressure(MAP) among the three groups. 2.Influnce of NDLIP on the cell injury after I/RAfter anesthesia,there was no significant difference on cTnI content among the three groups.At 120 min of reperfusion,compared with I/R group, cTnI content were significantly lower in both EMIP group and NDLIP group (P＜0.01),there was no significant difference between the latter two groups. Compared with pre-ligation,cTnI content was increased significantly in I/R group(P＜0.01) and showed a upward trend in the other two groups at 120-minute of reperfusion.Compared with I/R group,EMIP and NDLIP could diminish infarct size(IS:70.23±28.02 mg vs 30.58±3.54 mg and 36.73±17.57 mg,respectively,P＜0.01;IS/AAR:36.55±7.4%vs 18.75±9.04%and 20.77±9.93%,respectively,P＜0.01).3.Influnce of NDLIP on the oxidation - antioxidant system after I/RCompared with I/R group,EMIP and NDLIP could increase T-SOD activity(75.89±2.96 U/mgprot vs 84.53+5.41 U/mgprot and 87.67±4.29 U/mgprot,respectively,P＜0.01 ) and Mn-SOD activity(18.18±2.49 U/mgprot vs 24.56±3.76 U/mgprot and 27.16±5.9 U/mgprot,respectively,P＜0.01) and expression of Mn-SOD(Mn-SOD/β-actin:63±10%vs 94±9%and 97±9%, respectively,P＜0.01),and decrease MDA content(6.53±1.32 nmol/mgprot vs 4.8±0.54 nmol/mgprot and 4.32±0.73 nmol/mgprot,respectively,P＜0.01). There was no significant difference between EMIP group and NDLIP group.Conclusion:NDLIP can lower ST-segment,delay onset and shorten duration of VPC,decrease incidence of VA and cTnI content,reduce myocardial IS caused by I/R injury,and increase antioxidative ability of myocardium in diabetic rats.