The Protection Role Of Inhibiting Complex IV Against Myocardium Ischemia/Reperfusion Injury

Object: To investigated the role of inhibiting Complex IV during ischemia-reperfusion injury, respiratory chain is inhibited by CN^- and observe the reactive oxygen species production rate from mitochondria, alteration of respiratory chain and content of cardiolipin during ischemia-reperfusion.Method: Langendorff apparatus, ST.Thomas cardioplegic solutions containing KCN (KCN buffer) and Kerbs-Henseleit buffer(K-H buffer) containing hydroxocobalamin (VB₁₂ buffer) were used to establish the model of myocardial ischemia-reperfusion injury. SD rats were randomly divided into 7 groups(8 rats in each group): Balance group(B), Continuous group(C), Control group(CON), KCN buffer arrest group(KCN), Ischemia group(IS), KCN buffer arrest plus VB12 buffer reperfusion group(KVB), Ischemia plus VB₁₂ buffer reperfusion group(VB). All Hearts isolated from SD rats were mounted on a Langendorff apparatus and started with a 15 min perfusion for equilibration; Group B stop perfusion after equilibration. Group C went on perfusion for another 70 minutes after equilibration; Group KCN administrated KCN buffer followed by 40 minutes global ischemia; Group IS administrated ST.Thomas cardioplegic solutions followed by 40 minutes global ischemia; Group CON reperfused K-H buffer 30 min following the treatment of the Group IS; Group VB's treatment were like Group CON except reperfused VB₁₂ buffer 30 min instead of K-H buffer; Group KVB reperfused VB₁₂ buffer 30 min following the treatment of the Group KCN. The following parameters weres measured: 1 .The recovery of myocardial function, infarction size, activity of CK and LDH; 2. Parameters of mitochondrial respiratory chain, production rate of ROS from mitochondrial, and mitochondrial membrane potentials; 3. mitochondrial lipids were extracted and cardiolipin were determined with HPLC.Results: At the end of reperfusion, the parameters of myocardial function of goup KVB were better than CON, with less infarction size, and lower elevation degree of CK and LDH. No matter malic acid plus glutamic acid or succinic acid as the substrate, mitochondrial production rate of ROS from Group KCN was slower than IS at the end of ischemia period; and KVB slower than CON at the end of reperfusion with better parameters of mitochondrial respiratory chain, higher mitochondrial membrane potentials. KCN buffer reduced loss of cardiolipin at the end of ischemia and reperfusion.Conclusion: Adminstration CN^- to inhibition respiratory chain during ischemia reduced infarction size resulted from ischemia-reperfion injury; and conserved better function of mitochondrial and more cardiolipin after reperfusion; the inhibition of respiratory chain Complex IV may be one of the common mechanisms of sensing endogenous gas signal moleculs.