Abstract: Objective To explore the role of myeloperoxidase (MPO) and tumor necrosis factor-α (TNF-α) in myocardial injury
induced by hind-limb ischemia-reperfusion (IR) in rats. Methods Rat models of bilateral hindlimb IR established using a
tourniquet were randomized into 9 groups, including a normal control group normal, 2 ischemic groups with hindlimb
ischemia for 2 and 4 h, and 6 IR groups with a 4-h ischemia followed by reperfusion for 0.5, 2, 4, 6, 12, and 24 h. The plasma
and myocardial levels of MPO and TNF-α in each group were measured, and the myocardial expression of TNF-α was
determined with immunohistochemistry. Results Compared with the normal control group, the rats with a 2-h ischemia
showed significantly increased levels of MPO and TNF-α in the plasma and myocardium. Compared with those in rats with a
4-h ischemia, the plasma and myocardial MPO levels increased significantly at 0.5 and 2 h of reperfusion, respectively; the
plasma TNF-α level increased significantly at 4 h of reperfusion and myocardial TNF-α level decreased obviously at 12 h;
plasma levels of MPO and TNF-α both significantly decreased at 24 h. The plasma MPO and TNF-α and myocardial TNF-α
reached the peak levels at 4 h of reperfusion, and the peak myocardial MPO level occurred at 6 h. Immunohistochemistry
showed that TNF-α positivity moderately increased after hindlimb ischemia, and further increased at 4 h of reperfusion but
obviously reduced at 24 h. Conclusion The activation of systemic and local neutrophils and inflammatory cytokines may play
an important role in myocardial injury induced by hindlimb IR in rats.