Protection Of Heat Shock Protein 70 On Isolated Rat Heart

Objects: To investigate the protective effects of heat shock protein 70(HSP70) onisolated rat heart and the possible mechanism of this protection.Methods: 18 male Wistar rats of weight in 250～350 g were randomly divided into 2groups. Control group (C, n=9), Normal saline 0.5 ml was injected intraperitoneallyand 24 hours later isolated hearts were stored in 4℃for 3 hours withHistidine-tryptophan-ketoglutarate (HTK) solutions, and then isolated hearts wereperfused for 2 hours with Krebs-Henseleit (K-H) solutions by Langendorff model.Experimental group (E, n=9), Noradrenaline Bitartrate 3.1μmol/kg(0.53mg/kg) wasinjected intraperitoneally and 24 hours later isolated hearts were stored in 4℃for 3hours with HTK, and then isolated hearts were perfused for 2 hours withKrebs-Henseleit (K-H) solutions by Langendorff model. Myocardial HSP70 contentand the related biochemical indicators such as SOD,MDA,NO,NOS,CK,LDH,MWC were detected. The TdT-mediated dUTP nick end labeling(TUNEL) methodwas used to detect apoptotic myocytes in different groups. Bax and Bcl-2 expressionin myocardium were analyzed by immunohistochemical technique, and myocardialultrastructure were observed.Results: HSP70 in E group are higher than those in C group (t=17.96,P＜0.01). Biochemical indicators in E group are better than those in C group inisolated rat hearts: CK,LDH leakage of 10 minute, MWC, MDA content in E groupare lower than those in C group (t=4.13～15.81,P＜0.01), SOD activity,NO,NOScontents in E group are higher than those in C group (t=4.96～10.89,P＜0.01).Myocardial apoptosis rate in E group are lower than those in C group(t=7.066, P＜0.01). The expression of apoptosis related proteins Bcl-2 in E group(t=5.217,P＜0.01) is higher than that in C group and Bax in E group is lower than thatin C group (t=9.883, P＜0.01). The ultrastructural changes of myocardium of twogroups were observed, and it is better in E group than in C group.Conclusion: Noradrenaline Bitartrate injected intraperitoneally can induce the highexpression of heat shock protein 70,it plays a protective role in the isolated rathearts,it can improve the structure and function of myocytes in isolated rat hearts.HSP70 can decrease the MDA level and increase the SOD activity to enhancemyocardium's own ability to resist oxidative damage. It can protect myocardium cellsby improving the NO,NOS expression of myocardium cells and decrease myocardial apoptosis, furthermore, the protection of inhibiting myocardial apoptosis may berelated with apoptosis related proteins Bcl-2,Bax.