Effect Of Ischemic Postconditioning With Different Protocols On Skeletal Muscle Ischemia Reperfusion Injury In A Rat Model

Objectives:To investigate whether ischemic postconditioning can induce protection against skeletal muscle ischemia/reperfusion(I/R) injury in a rat model and select an optimal protocol for further investigation. And to preliminary investigate the mechanism of ischemic postconditioning on skeletal muscle ischemia/reperfusion injury.Methods:Adult male Sprague-Dawley rats were randomly allocated into four groups(n=9):one for I/R group and the other three for postconditioned groups (PostA, Post B, and Post C). The animals were subjected to 4-hr of main ischemia by occlusion of the femoral artery and followed by 24-hr reperfusion. Postconditioning was applied at the onset of reperfusion using three different algorithms:4 cycles of 10-sec R/I(Post A),4 cycles of 30-sec R/I(Post B), and 4 cycles of 60-sec R/I (PostC). All operations were carried out in right limbs for ischemia/reperfusion experiment and in left limbs for sham. At the end of 24-hr reperfusion blood samples were taken from femoral vein for serum lactate dehydrogenase(LDH), and tissue samples from gastrocnemius or tibialis anterior muscle for wet/dry ratio (W/D), myeloperoxidase (MPO), malondialdehyde (MDA), and ultrastructure observation under electron microscope.Results:The W/D in IRI was much increased statistically(P<0.05 vs sham);The W/D in PostB was much decreased statistically(P<0.05 vs I/R), while no significant statisticaldifference displayed in Post A or PostC (P>0.05 vs I/R); The serum LDH, tissue MPO and MDA in PostA,Post B and PostC were all uniformly lower compared to I/R (P< 0.05), and no significant statistical differences were seen among the three postconditioned groups(P>0.05); Under electron microscope the mitochondria ridge, myofibril structure and integrity of the nucleus displayed in muscular cells were more intact in PostA,PostB, and PostC compared to I/R, and the outcome in Post B was the best.Conclusion:Taken together, ischemic postconditioning can endow endogenous protection against skeletal muscle I/R injury and the protocol with 4 cycles of 30-sec R/I is optimal and can be used for further study. The mechanism of ischemic postconditioning on protecting the skeletal muscle I/R injury is mainly by reducing reactive oxygen species generation, relieving muscle fiber edema, neutrophil aggregation, energy metabolism.