Study On Dynamic PH Measurement Of Rat Skeletal Muscle Undergoing Ischemic Postconditioning And Simulating Infusion With Acidic Perfusate To Attenuate Ischemia Reperfusion Injury

Background: Recent studies have reported,an important mechanism of myocardial ischemia postconditioning was protected by maintain early perfusion acidosis to 3min.But the specific p H changes and how to simulate the acidic perfusion reduce ischemia reperfusion injury is still not seen.Similar studies on skeletal muscle are also not seen.Objectives : To measure the dynamic p H of rat skeletal muscle undergoing ischemic postconditioning,to infuse with acidic perfusate in rats simulating the p H curve and investigate its effect on ischemia reperfusion injury.Methods : Based on the ischemia reperfusion injury model and optimized ischemic postconditioning protocol in previous study.Dynamic p H measurement of rat skeletal muscle was carried out using optical fiber p H instrument in main ischemia period,4 cycles of 30 s reperfusion/ 30 s ischemic postconditioning period,and reperfusion period.The acidic perfusate equivalent to p H in ischemic postconditioning period was prepared with lactic acid and saline for simulating infusion.25 healthy adult male Sprague-Dawley rats were randomly divided into five groups(n=5): Sham group,ischemia reperfusion(IR)group,ischemic postconditioning(IPo C)group,acidic perfusate(Lac)group,and normal saline(NS)group.Blood samples were collected in each group after the IR respective experiments for detection of lactate dehydrogenase(LDH).The samples from gastrocnemius were harvested and wet/dry ratios(W/D ratio)were calculated,levels of myeloperoxidase(MPO)were assayed,and infarct sizes were measured with 2,3,5—triphenyltetrazole chloride(TTC)staining.The samples from tibialis anterior were also harvested for analysis of the key protein Erk1/2 in the MAPK pathway by western blot.Results: A prolonged acidic platform was detected in the early reperfusion during ischemic postconditioning process,on which the p H was 6.81±0.133,and the duration was 2 minutes 40 seconds.The results of LDH、MPO、W/D ratio showed that there were significantly lower levels in both Lac group and IPo C group compared with IR group(P<0.05),but no significant difference between Lac infusion group and IPo C group(P > 0.05).The results of Western Blot demonstrated that there was no significant difference in the expression of Erk1/2among the five groups(P>0.05),however,the expressions of p-Erk were significantly higher in Lac infusion group,IPo C group,and NS infusion group compared with IR group(P<0.01).No significant difference was displayed between Lac group and IPo C group(P> 0.05)but significantly increased p-Erk in Lac infusion group and IPo C group compared with NS infusion group(P<0.05).TTC staining showed that the infarct sizes in IPo C group and Lac group were significantly reduced compared with IR group(P<0.05).Conclusion: A prolonged acidosis is still maintained during ischemic postconditioning in early reperfusion and acidic perfusate simulating ischemic postconditioning effectively attenuates ischemia reperfusion injury in rat skeletal muscle.The underlying mechanism may act directly on MPTP to avoid its immediate opening,or associate with activation of Erk1/2 in RISK signaling pathway to trigger protection.