Ischemic Preconditioning Protects Mitochondrial Respiratory Function In Complex I With Decreased Free Radical Production

Abstract

Mitochondrial respiratory complexes are damaged by ischemia reperfusion injury. Oxygen free radicals (OFR) may be involved in the cardioprotective mechanism of ischemic preconditioning (IPC). The purpose of this study was to determine the effects of IPC on mitochondrial respiratory complex I activity and OFR production.Rat hearts (n=6/group) were subjected to either A) 30 minutes (min) of equilibration (EQ), 30 min of ischemia (I), and 30 min of reperfusion (R) (CONTROL) or B) 10 min of EQ, three 5 min episodes of IPC, 30 min I, and 30 min of R (IPC group). A third set of non‐ischemic control hearts were also studied (NIC). Mitochondria were isolated at end reperfusion. Respiratory complex I activity was assessed by polarography using specific substrates and inhibitors for complex I in the presence of ADP. Complex I OFR production was measured by Electron Paramagnetic Resonance (EPR) spectrometry. Complex I substrates were glutamate and malate (4.7 mM) and the inhibitor was rotenone (188 nM). Data is expressed as mean±SEM.Ischemia reperfusion impairs mitochondrial complex I activity and increases complex I OFR production. IPC preserves mitochondrial respiratory complex I activity and decreases mitochondrial free radical generation at end reperfusion.