| Objective:Establishment of rabbit acute myocardial ischemia-reperfusion model, by myocardialcontrast echocardiography to observe the effect of ischemic postconditioning onmyocardial microcirculation, and to explore its mechanism of action.Methods:100New Zealand white rabbits were randomly divided into sham operation group,myocardial infarction group, ischemia reperfusion group, ischemic postconditioning groupand ischemic postconditioning+Znpp group, with20rats in each group. Sham operationgroups only thoracotomy without ligation, threading and inserted in the left anteriordescendingartery(LAD); Acute myocardial infarction groups ligate LAD directly before chest closure;In reperfusion groups ligate LAD in1hours and reperfuse2hours before chest closure;Ischemic postconditioning groups ligate LAD for1hours and reperfusion for30seconds,was30seconds (4times),2hours of reperfusion before chest closure; Ischemicpostconditioning+Znpp groups ligate after ZnPP0.2mg/kg injection in10minutes, YuBuzhou with the IPostC group and another step is same as Ischemic postconditioninggroup. Continuous ECG is monitored during operation. And respectively we record ⅠleadECG before ligating LAD, after ligating LAD10minutes and2hours after reperfusion.Each rabbit collects3ml blood samples in open chest,3hours after ligation andexperiment after1weeks ago by femoral vein or jugular vein. We determinate theconcentration of serum troponin I, high sensitive C-reactive protein, SOD and MDA. After1weeks, rabbits were examinated by echocardiography and myocardial contrastechocardiography, were analyzed offline application by EchoPAC-7ultrasound imageworkstation and we obtain images. We isolate left ventricular myocardium after anesthesiarabbits by inject3%pentobarbital sodium solution through ear intravenous.5heartspecimens in coronary wear line under the5mm clipping a small piece of left ventricularmyocardial tissue morphological examination and determination of infarct size.15hearttissues determinate the Nrf2and HO-1protein concentration by means of Western Blot.Results:1. The rabbit is no difference in body weight and sex (P>0.05)2. Four groups of ECG vascular ligation were seen in lead ST segment arch lift，3hoursof ECG of four groups were observed after ligation of ST segment drop, there was nosignificant difference about>50%ST segment drop in each group (P>0.05)3. The value of serum cardiac troponin I in before the ligation groups had no significantdifference between the four groups of troponin I, was higher than that in shamoperation group, ischemia group after ligation four adaptation of cardiac troponin Ilower than the other three groups, there were significant differences (P<0.05), itsadvantage into a week later.4. Serum high sensitivity C-reactive protein in ligation group ischemia postconditioninggroup concentration lower than the other three groups, there was significant difference(P<0.05), no significant difference (P>0.05) after a week.5. Serum superoxide dismutase to concentration of ischemia postconditioning group andischemia postconditioning+Znpp group was higher than ischemia reperfusion group,myocardial infarction group in ligation group after3hours of ischemia,there was asignificant difference (P<0.05), its advantage into a week later.6. Serum levels of malondialdehyde in ligation group, postconditioning group ofmalondialdehyde was lower than the other three groups, there was significantdifference (P<0.05), there was no significant difference after a week(P>0.05).7. Analysis of left ventricular short axis view by myocardial contrast echocardiography quantitative: The front wall, anterolateral wall, anterior septal, underside wall, inferiorwall and inferior septum, posterior septal A value, B value and AB value were nosignificant difference(P<0.05). The front wall, anterolateral wall, anterior septal andunderside wall, inferior wall and inferior septum, posterior septal A value, B value andA×B values were significantly different in four ligation groups(P<0.05). The frontwall, anterolateral wall, anterior septal comparison ischemic postconditioning groupand myocardial infarction, ischemic reperfusion and ischemic postconditioning+ZnppA value, B value and A×B value were significantly different in four ligation groups.(P<0.05)8. Analysis of left ventricular short axis view of myocardial segment of circumferentialstrain：Ischemic postconditioning group front wall, anterolateral wall and anteriorseptum circumferential strain peak value was higher than that of myocardial infarctiongroup, ischemia reperfusion group and ischemic postconditioning+Znpp groups, therewas significant difference(P<0.05). Myocardial infarction group, ischemia reperfusiongroup and ischemic postconditioning+Znpp, the circumferential strain of front wall,anterolateral wall and anterior septum were no significant difference (P>0.05).9. The area of myocardial infarction: infarction area of ischemic postconditioning groupis less than the other three groups in four ligation ischemia group, there weresignificant differences (P<0.05).10. Light microscopic examination was performed in four groups. Damage of ischemicpostconditioning group was lighter than other three groups; Leave no thrombus andcontrast agent storage vessels in normal myocardial tissue.11. Expression of Nrf2protein of myocardial cells: Sham operation group, myocardialinfarction, expression of Nrf2was significantly lower than that in ischemia reperfusion,ischemic postconditioning and ischemic postconditioning+Znpp (P<0.05); Ischemicpostconditioning and ischemic postconditioning+Znpp Nrf2expression wassignificantly higher than that in ischemia reperfusion group (P<0.05); Ischemicpostconditioning and ischemic postconditioning+Znpp Nrf2expression had no differences(P>0.05).12. HO-1protein expression in cardiac myocytes: HO-2protein expression of ischemicpostconditioning group, ischemia reperfusion group was significantly higher than shamoperation, myocardial infarction and ischemic postconditioning group+Znpp (P<0.05);HO-2protein expression of ischemic postconditioning group was significantly higherthan ischemia reperfusion group (P<0.05); Expression of HO-1protein in ischemicpostconditioning group+Znpp group had no significant difference to myocardialinfarction group and sham operation(P>0.05).Conclusion:1. Through the quantitative myocardial contrast echocardiography analysis showed thatischemic preconditioning can improve the myocardial infarction myocardialmicrocirculation.2. Myocardial contrast echocardiography examination is safe and feasible.3. The Nrf2and HO-1pathways are involved in mediating ischemic postconditioning onmyocardial protection after myocardial infarction. |
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