| Objective : Cardiomyopeptidin (CMP) is a kind of small molecular weight polypeptide extracted from the sucking porcine hearts. It was indicated, in the previous experiments, that CMP could prevent and treat ischemia-induced myocardial injury.This study aimed to confirm the protective affect of CMP on myocardial ischemia-reperfusion injury and discuss the possible mechanisms, by establishing the neonatal rabits myocardial ishemia-reperfusion injury model ex vivo and investing the effect of different dosage used to the immature myocardial ischemical reperfusion injur of neonatal rabits. It aimed to search an excellent myocardial preservation method for the infant in clinical.Methods:This study used the neonatal rabits myocardial ishemia-reperfusion injury model ex vivo, observating the heart functional parameter ,changes of myocardial enzymes and ultramicrostructure, myocardial cell apoptosis after 120 minutes ischemia and 20 minutes reperfusion.It aimed to evaluate the effect of CMP on neonatal rabits myocardial ischemia-reperfusion injury .This study established the neonatal rabits myocardial ishemia-reperfusion injury model using Langendorf isolated heart perfusion system.Thirty-two pure breed New Zealand neonatal rabits of 3-4 weeks were divided into four groups, control group A which were only used cool crystalline body of St thomas cardioplegic solution to perfuse during the ischemia and experiment B, which were added to some dosage of CMP .Each of isolated heart was applied by whole heart cool ischemia after 4℃and120 minutes, then 37℃,60minutes of reperfusion.And group B were divided into three groups according to the different dosage of CMP: B1,B2,B3.This study was aimed to detect the heart functional parameter by ALC-MPA multichannel biology signal analysis system when in the 15min,30min.60min : HR, LVPSP, left ventricular pressure upgrade max(+dp/dtmax), corona flow postischemia 15 min ,CK ,LDH;the concentration of MDA,SOD and ATP on the left ventricle constitution; the changes of myocardial ultramicrostructure by light microscope and electron microscope; calculating myocardial cell apoptotic index by TUNEL.Results: 1. Before the ischemic,experiment and control groups had no significant differences (P>0.05) on the heat functional parameter(HR,LVPSP,+dp/dtmax,CF);Reperfusion, the heart function recovery of experiment group of 15min,30min,60min were better than control group, especially in B2,B3. 2. Before the ischemic,experiment and control groups had no significant differences (P>0.05) on the Ck,CK-MB,LDH. The values of Ck,CK-MB,LDH dropped obviously (P<0.05),especially in B2,B3(P<0.05).3. It had statistic differences of the values of ATP, MDA and SOD while comparing experiment groups and control groups (P<0.05). the values of ATP,SOD increased more distinctly (p<0.05)while droped in control groups(p<0.05),especially groupsB2 and B3 change more distinctly, especially in B3.4. Myocardial ishemia-reperfusion placed a premium on the apoptosis of cardiac muscle cell. No signs of apoptosis of cardiac muscle cell in group B1 and control group were found and no statistic differences of AI (P>0.05) were presented. While the apoptosis of cardiac muscle cell were obviously found in group B2,B3 and statistic differences of AI (P<0.05) were presented, group B3 was the minimum and had significant statistic differences of AI (P<0.01).5. under the light microscope and electron microscope,the injury of control group myocardial pathology changed obviously ,the injury of ultramicrostructure was lightened compared with experiment group and control group ,especially group B2 and B3。Conclutions: (1)CMP could improve heart rate or the ventricular fibrillation,descrease cardiac enzymes leakage and induce Oxygen Free Radical (OFR) ,improve the ability of cardiac muscle cell energy metabolism , relieve the injure of the cardiac muscle ultramicrostructure. (2)CMP had the protection effective to the Neonatal Rabbits after myocardial ischemia-reperfusion injury. the protection effective of CMP on neonatal rabits after myocardial ischemia-reperfusion injury was relatived with the dosage.the more dosage,the more significant protection effective.
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