The Late Phase Preservation Of Dexamethasone Pretreatment On Stunning Myocardium

Objective:To assess dexamethasone ,as a pretreatment drug, whether or not can protect stunning myocardium in the late phase of pretreatment and discuss the mechanisms about the myocardial preservation.Method:we modeled myocardial stunning model by ischemia 15min and reperfusion 45min in living rat.30 Wistar rats (270-290g) were separated Sham group,I/R group and Treat group in random.The rats in Treat were injected dexamethasone (0.3ml/kg ,im) at 24h and 12h before operation.The other were injected Saline (0.3ml/kg, im) at 24h and 12h before operation. Capturing HR, LVSP,LVDP, dp/dt,and -dp/dt at ischemia,ischemic 15 min,reperfusion 1,5,15,30,45min,Assaying the content of CK-MB,LDH in blood serum,the content of MDA and HSP70 in myocardiu m,Observing ECG and histology change were compared among Sham group,I/R group and Treat group.Results:In reperfusion1,5,15,30min, LVSP,dp/dt and -dp/dt have significant of difference in I/R and Treat group(p<0.05),Treat group was higher than I/R group.In Treat and I/R,the Content of CK-MB,LDH, MDA were higher than Sham group(p<0.05), the I/R group was highest in 3 groups(p<0.05).But comparing I/R group, the content of HSP70 in ischemic myocardium was obviously increased in Treat group(p<0.01),however, the content of neutrophilic granulocyte were fewer in Treat group(p>0.10). Conclusion: Dexamethasone pretreatment can obviously decrease the injury of stunning myocardium, promote recovery of myocardial function.The myocardial preservation occur in the late paste of pretreatment,18-24h after dexamethasone pretreatment.The preservation perhaps come true by a great quantity of HSP70 Expressing in myocardium. Dexamethasone pretreatment is worth of investing method of myocardial preservation in clinic.