This study investigated the effect of myocardial ischemic postconditioning (IPostC) and pharmacologic postconditioning by cyclosporine A on the changes in capacity of oxidative phosphorylation, and coupling between adenine nucleotide translocase (ANT) and mitochondrial creatine kinase (miCK).Methods
Isolated perfused hearts from C57BL/6J mice were subjected to 40-min of ischemia followed by 20-min of reperfusion (Control group). Hearts were divided into 4 groups: 1) Control; 2) IPostC: elicited by ten cycles of 5-s ischemia/5-s reperfusion after the 40-min ischemia; 3) cyclosporine A : administered during the first min of reperfusion; 4) Sham: perfusion with normoxic condition (n = 6 in each group). Parameters of mitochondrial function were assessed on saponin-skinned fibers from isolated hearts. The protocol of the respiration rate determination included a cytochrome c test to check the intactness of the outer mitochondrial membrane. The apparent affinity of the mitochondrial oxidative phosphorylation system for ADP (Km) in the presence and absence of creatine were also evaluated to test the ANT-miCK functional coupling.Results
Our results show that the capacity of oxidative phosphorylation was significantly reduced in control and cyclosporine A groups, and equivalent in IPostC group in comparison to Sham group. The cytochrome c test was negative in IPostC and cyclosporine A groups, suggesting intact outer mitochondrial membrane ; and positive in control group, suggesting some alteration of the outer mitochondrial membrane. In Sham and IPostC groups, Km is high and addition of creatine significantly decreases Km, suggesting a high efficiency of the ANT-miCK functional coupling. Alterations in mitochondrial function in control and cyclosporine A groups were characterized by a significant decrease in Km and partially loss of the stimulatory effect of creatine.Conclusions
IPostC and cyclosporine A prevent the loss of integrity of the outer mitochondrial membrane after prolonged ischemia, moreover IPostC contribute to the preservation of the ANT-miCK functional coupling.