Effects Of Ischemic Postconditioning On Cmyocardialapoptosis And Expression Of Related Gene Protein In Myocardialischemic Reperfusion In Rats

Objective:To observe the effects of ischemic postconditioning on myocardial apoptosis and the expression of Bcl-2,Bax in myocardial ischemia-reperfusion injury;meanwhile to observe adding effects of postconditioning and preconditioning in order to study mechanisms of cardioprotective effects of ischemic postconditioning .Methods:Myocardial ischemia-reperfusion injury model in vivo was established.Forty-eight healthy SD rats were selected and randomly divided into 4 groups: Group IR (ischemia reperfusion group,n=12): the rat hearts were subjected to 40 minutes of LAD occlusion and 120 minutes of reperfusion;Group IPC (preconditioning group,n=12):with 3 cycles of 5 minutes of ischemia,each followed by 5 minutes of reperfusion,then followed IR group;Group IPO(postconditioning group,n=12): with 40 minutes ischemia followed by 120 minutes reperfusion,reperfusion was initiated for 30 seconds of reperfusion followed by 30 seconds of reocclusion, repeated for 3 cycles; Group IPC+IPO (preconditioning+postconditioning group,n=12): with protocol similar to that of IPO group except for 3 round 10 minutes ischemic preconditioning applied before 40minutes ischemia. the changes of myocardial ultramicrostructure by light microscope and electron microscope; The area of myocardial infarction was measured by TTC; Reverse transcription polymerase chain reaction(RT-PCR)was used to detected the expression of Bcl-2,Bax mRNA,while protein expression ofBcl-2,Bax was detected with immunohistochemistry; Apoptotic cell death in myocardium were determined by in situ terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end Iabeling(TUNEL) and apoptosis index (AI)were analyzed.Results:1. Under the light microscope and electron microscope, the injury of ultramicrostructure in IPC,IPO and IPC+IPO group was lightened obviously compared with IR group, but there was alike or similar morphology change in IPC,IPO and IPC+IPO group. 2. The area of myocardial infarction in IPC,IPO and IPC+IPO group was signifieantly lower than that in IR group(p<0.05),but there was no significant difference among IPC,IPO and IPC+IPO group.3. The AI in IPC,IPO and IPC+IPO group was signifieantly lower than that in IR group(p<0.05), Therew as no significant difference among IPC,IPO and IPC+IPO group.4. The expression of Bcl-2 mRNA in IPC,IPO and IPC+IPO group was signifieantly higher than that in IR group(p<0.05);The expression of Bax mRNA in IPC,IPO and IPC+IPO group was signifieantly lower than that in IR group(p<0.05);There was no significant difference among IPC,IPO and IPC+IPO group in the above parameters.5. The expression of Bcl-2 in IPC,IPO and IPC+IPO group was signifieantly higher than that in IR group(p<0.05);The expression of Bax in IPC,IPO and IPC+IPO group was signifieantly lower than that in IR group(p<0.05);There was no significant difference among IPC,IPO and IPC+IPO group in the above parameters.Conclusions:1. Ischemic postconditioning,like ischemic preconditioning,could obviously decreases myocardial apoptosis induced by ischemia reperfusion injury,which may contribute partly to the ultimate reduction of myocardial infarction in acute myocardial ischemia reperfusion.2. The reduction of myocardial apoptosis rate is associated with increase the expression of Bcl-2 and decrease the expression of Bax.3. Myocardial protection with ischemic postconditioning is not enhanced by ischemic preconditioning.