Protective Effects Of Noninvasive Delayed Limb Ischemic Preconditioning Against Myocardial Ischemia-reperfusion Oxidative Injury In Rats

Objective:To study the protective effects of noninvasive delayed limb ischemic preconditioning against myocardial ischemia-reperfusion oxidative injury in rats.Method:Wistar rats were divided randomly into ischemia-reperfusion (I/R),early myocardiac ischemic preconditioning(EMIP)and noninvasive delayed limb ischemic preconditioning(NDLIP)groups.Rats in NDLIP group were subjected to NDLIP for 3 days.On the forth day,all rats were subjected to myocardial ischemia/reperfusion injury.Rats in EMIP group were preconditioned before ischemia.ECG and myocardial infarct size were examined.Activity of superoxide dismutase(SOD),glutathione peroxidase (GSH-PX),xanthine oxidase(XOD)and concentration of malondialdehyde (MDA)were measured.Total RNA was extracted from the hearts and the Mn-SOD mRNA expression in cardiomyocytes was studied by the method of reverse transcription polymerase chain reaction(RT-PCR).Results:①Compared with I/R group(0.488±0.093 mV),EMIP and NDLIP could lower the raise degree of ST-segment(0.368±0.066 and 0.335±0.078 mV,P＜0.01 and P＜0.01)during the periods of ischemia.The onset of VPC was early(5.60±1.64 min),the duration was long(11.47±2.51 min)in I/R group.EMIP and NDLIP could delay the onset of VPC(12.03±1.87 and 7.62±0.67 min,P＜0.01 and P＜0.01),shorten duration(5.13±2.18 and 7.01±1.97 min,P＜0.01 and P＜0.01),and decrease incidence rate of VT and VF.②Compared with I/R group's IS(65.36±19.48mg)and IS/AAR(30.2±8.2%), EMIP and NDLIP could reduce IS(38.01±11.07 and 42.09±16.21mg, P＜0.01 and P＜0.01),decrease IS/AAR(19.0±5.9%and 21.4±9.4%,P＜0.05 and P＜0.05).③Compared with I/R group's total SOD(143.19±18.28 U/mgprot)and Mn-SOD(44.63±11.52 U/mgprot),EMIP and NDLIP could increase total SOD activity(162.26±6.41 and 158.71±12.98 U/mgprot, P＜0.05 and P＜0.05)and Mn-SOD activity(76.49±17.57 and 76.80±2.62 U/mgprot,P＜0.01 and P＜0.01);Compared with I/R group(76.70±6.37), EMIP and NDLIP could elevate GSH-PX activity(90.62±9.80 and 93.55±8.30,P＜0.01 and P＜0.01);Compared with I/R group(89.18±10.95 U/gprot), NDLIP could decrease XOD activity(75.15±7.15 U/gprot,P＜0.01); Compared with I/R group(1.99±0.15 nmol/mgprot),EMIP and NDLIP could decrease concentration of MDA(1.79±0.18 and 1.66±0.12 nmol/mgprot, P＜0.05 and P＜0.01);Among all these oxidative and antioxidative substancese, there was no significance between EMIP and NDLIP.④The RT-PCR results indicated that compared with I/R group,expression of Mn-SOD were increased in EMIP and NDLIP group.But there was no significant difference between EMIP and NDLIP group.Conclusion:NDLIP can reduce ST-segment,delay onset,shorten duration of VPC and decrease incidence rate of VT and VF,which is nearly to the level of early myocardiac ischemic preconditioning;NDLIP can decrease IS caused by ischemia-reperfusion injury(IRI);protect cardiac cell against IRI through elevating tolal SOD,Mn-SOD and GSH-PX activity,decrease XOD activity and concentration of MDA;increase the expression of Mn-SOD. In short,the protective effects of NDLIP against myocardial ischemia-reperfusion oxidative injury are similar to those of EMIP,the protective effects are associated with the increase in antioxidative ability of myocardium.