Inhibition Of Apoptosis And Protection Of Myocyte Membrane Protein By Ischemic Preconditioning During Cardiopulmonary Bypass

Based on the stable and reliable feline heart's cardiopulmonary bypass (CPB) model, theprotective effects of myocyte membrane proteins and internal environment and inhibition ofapoptosis by ischemic preconditioning (IPC) from ischemia/reperfusion (IR) injury wereobserved by some advanced methods such as flow cytometry, electron paramagneticresonance, atomic absorption spectroscopy and freeze-replica, et al. Furthermore, therelationship among myocyte membrane proteins, signal transduction and apoptosis was alsoelucidated. The main methods and results are described as follows: 1. Establishment of feline heart's model and study on cardiac function andmyocardial pathological and ultrastructural alterations during CPB Ninety felines were randomized into three groups: Control group, in which CPB wasconducted without aortic cross-clamping (ACC); IR group, with 60 min ACC followed by 90min reperfusion, and cardioplegia used during period of ACC; IPC group, with protocolsimilar to that of IR group except for three-round 15 min IPC applied before ACC. Decreased LVSP, dp/dt max and dp/dt min were found during reperfusion period in bothIR group and IPC group as compared to that of Control group (P<0.05). However, LVSP,dp/dt max and dp/dt min in IPC group were significantly higher than that in IR group(P<0.05). Then there were obvious recovery tendency at 90 min after reperfusion in both IRgroup and IPC group. The ischemic and denaturation changes of myocardium were evaluated by the modifiedhaematoxylin fuchsin basic picric acid (HBFP) special pathologic staining and the modifiedGonori chromotropic acid (GCA) special pathologic staining respectively. Diffuse HBFP andGCA positive staining were observed in myocardium of IR group. However, only focalpositive staining appeared in that of IPC group. There were significant differences between IRgroup and IPC group in positive strain density (P<0.05). 5第二军医大学 英文摘要 博士学位论文 The ultrastructural changes of myocyte were observed under electron microscope.During ACC period, the most significant ultrastructural changes were mitochondrial swellingand damage of capillary endothelium, which were more severe in IR group. Reperfusionfurther deteriorated the overall damage. At the time point of RP 30 min, the ultrastructuraldamages (Rainio scores) were evidently lower in IPC group than that in IR group (P<0.05).Then there were obvious recovery tendency at 90 min after reperfusion in both IR group andIPC group. 2. Protection of myocyte membrane proteins by IPC from ischemia andreperfusion injury during CPB The changes of myocyte membrane protein components were observed by SDS-PAGEelectrophoresis. Before ACC, the myocyte membrane protein SDS-PAGE patterns of allgroups were almost the same. Decreasing or even disappearing of membrane proteins, whichmolecular weights were less than 18 KDa, were observed in IR group and IPC group duringACC and reperfusion periods. There was a recovery tendency in IPC group at 90 min afterreperfusion. The alterations of membrane proteins' particles were observed by freeze-replicatechnique. The membrane protein's particles in E-facet of membrane were almost the sameamong all groups, but the membrane protein's particles in P-facet were different. Thenumbers of membrane proteins' particles were decreased significantly in IR group and IPCgroup during the periods of ACC and reperfusion (P<0.05). Then there were obvious recoveryin both IR group and IPC group. The electron paramagnetic resonance was used to characterize the myocyte membraneproteins conformation and movement, which described by the ratio of the strong solidity andweak solidity (hS / hW) and rotational correlation time ( c ) of membrane proteins ofspin-labeled sulfhydryl...