The Relationship Between Delayed Cardioprotection Induced By Ventricular Overdrive Pacing Preconditioning And Heat Shock Protein

Objective: To observe the expression of heat shock protein 70(HSP70) and heat shock protein 27(HSP27) in late phase of cardioprotection induced by ventricular overdrive pacing preconditioning, so as to explore the relationship between delayed cardioprotection of preconditioning and heat shock protein.Methods: 24 Newzealand rabbits were randomly divided into 3 groups: the control group, the pacing group and the Pacing + Actinomycin group, and 8 rabbits in each group. (1) control group : catheter was left in the right ventricle for 70 min and these rabbits under lasting ischemia and reperfusion by ligating left anterior descending branch of coronary artery after 24h. (2) pacing group: Right ventricular was exposed with overdrive pacing 24h before ischemia and reperfusion. (3) Pacing + Actinomycin group: Actinomycin D was injected with the dose of 0.1mg/kg, then followed the pacing group. During period of ischemia and reperfusion, the levels of creatine kinase(CK) and creatinine kinase isoenzyme(CK-MB) were monitored, and the electrocardiogram were recorded during the phase of reperfusion. HSP70 and HSP27 were tested by immunohistochemistry. Results: For comparsion of levels of CK and CK-MB, there were no differences among the three groups before ischemia (P>0.05). But they were significantly lower in the pacing group when compared with the control group at the different phases after ischemia (P<0.01), and those in the Pacing + Actinomycin group were between the above two groups. (P<0.01) (2) There were 5 cases in the control group which generated arrhythmia, and 4 cases in the Pacing + Actinomycin group, but no one in the pacing group. The occurrence rate of arrhythmia was significantly different between the control group and the pacing group. ((P<0.05) (3) The levels of HSP70 and HSP27 expression in the pacing group were significantly higher than those in the other two groups. (P<0.01)Conclusion: This experiment had successfully improved the animal model of ventricular overdrive pacing preconditioning in the use of micro-wound technology. And it confirmed that the overdrive pacing preconditioning could mimic the ischemic preconditioning. The delayed cardioprotection, including reducing the damage of myocardium and the occurrence of arrhythmia, had been observed in the ischemia and reperfusion phase. Meanwhile, the expression of HSP70 and HSP27 increased, which indicated that the delayed cardioprotection may have close correlation with the overexpression of HSP70 and HSP27.