Brief antecedent anoxia preserves mitochondrial function after sustained undersupply: A subcellular correlate to ischemic preconditioning?

Background : There is increasing evidence that mitochondria – owning a high degree of autonomy within the cell – might represent the target organelles of the myocardial protection afforded by ischemic preconditioning. It was the aim of the study to investigate a possible subcellular correlate to ischemic preconditioning at the mitochondrial level. In addition, we tested whether this protection depends on mitochondrial ATP-dependent potassium channels ( K ATP ) and an might involve an attenuation of mitochondrial ATP hydrolysis during sustained anoxia. Methods and Results : Sustained anoxia (A, 14 min) and reoxygenation (R) completely inhibited state 3 and state 4 respiration of isolated ventricular mitochondria from Wistar rats. An antecedent brief anoxic incubation (4 min) followed by reoxygenation (2 min) prevented this loss of mitochondrial function. The protection afforded by anoxic preconditioning could be mimicked by the K ATP opener diazoxide (30 μmol/l) and was completely inhibited by the K ATP blocker 5-hydroxydecanoic acid (300 μmol/l). Structural mitochondrial integrity, as estimated from externalization of the mitochondrial enzymes creatine kinase and glutamateoxalacetate transaminase, remained unchanged between the groups, as did mitochondrial ATP loss during anoxia. Conclusion : For the first time, we provide direct evidence for a subcellular preconditioning-like functional mitochondrial adaptation to sustained anoxia. This effect apparently depends on opening of K ATP but is independent of ATP preservation.