The aim of the present study was to investigate whether a gradually increasing reperfusion algorithm, in which the brief reperfusion was lengthened as the duration of each reperfusion/reocclusion cycle remained fixed, enhances cardioprotection. Rats were randomized into 5 groups: the sham, reperfusion injury (R/I), gradually decreased reperfusion (GDR; 30/10‑25/15‑15/25‑10/30 sec of reperfusion/reocclusion), equal reperfusion (ER; 4 20/20‑sec reperfusion/reocclusion cycles) and gradually increased reperfusion (GIR; 10/30‑15/25‑25/15‑30/10 sec of reperfusion/reocclusion). The rats were sacrificed to measure serum markers, apoptotic indices and infarct size. Western blot analyses were used to analyze the expression of molecules involved in important signaling pathways. All the three postconditioning patterns were found to provide cardioprotection (P<0.05 compared with the R/I group). GIR provided optimum cardioprotection, followed by ER and then GDR. Apoptotic index and serum marker levels were significantly reduced in the GIR compared with the ER group (P<0.05). The enhanced cardioprotection provided by GIR was accompanied by significantly increased levels of extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation and Bcl‑2, as well as lower levels of p38/c‑Jun N‑terminal kinase (JNK) phosphorylation, tumor necrosis factor α (TNFα), caspase‑8, Bax, caspase‑9 and cytochrome c (Cyt‑c) in the cytoplasm of rats (P<0.05, all compared with ER). The infarct size in the rats of the GIR group was also smaller compared with that in the rats of the ER group, but this difference was not significant (16.30±5.22 vs. 20.57±6.32%, P>0.05). All the variables measured in the present study were significantly improved in the GIR group compared with the GDR group (P<0.05). In conclusion, the association between brief reperfusion and reocclusion is an important factor in postconditioning algorithms. Additionally, GIR results in improved cardioprotection compared with that achieved by the remaining algorithms examined.
The effects of local myocardial administration of lactic acid and low-dose edaravone were investigated to determine if this combination provides benefits similar to mechanical postconditioning. We randomly divided 108 rats into 6 groups: sham, reperfusion injury, postconditioning (Post), lactic acid (Lac), low-dose edaravone (Eda), and lactic acid + low-dose edaravone (Lac+Eda). The left coronary arteries of the rats were occluded for 45 minutes, before the administration of the treatments. The rats were euthanized at different time points to examine the infarct size and serum markers of myocardial injury and apoptosis and measure the expression of signal pathway markers. We found that the infarct areas caused by ischemic-reperfusion injury were reduced largely by postconditioning and Lac+Eda injection; a similar trend was observed for serum markers of myocardial injury, apoptosis, and hemodynamic parameters. Compared with the Post group, the Lac+Eda group had similar blood pH values, levels of reactive oxygen species, mitochondrial absorbance, and levels of signal pathway marker. The Lac and Eda groups partly mimicked the protective role. These data suggest that local myocardial administration of lactic acid and low dose of edaravone initiates protective signal pathways of mechanical postconditioning and replicates the myocardial protection.
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