The Protection Of Adenosine Enriched Cardioplegia On Immature Myocardial Ischemia Reperfusion

ObjectiveMyocardial ischemia reperfusion injury(MIRI) is a common phenomenon in clinical practice.The exact mechanism is still unclear at present.The previous research results shows that apoptosis is one of the important procedures in happening of MIRI.Adenosine is one type of prine nucleoside,combined with adnine and ribose.It,s precursor and metoblic product of AMP and widly dispersed in many kinds of tissues.Adenosine has the properties of slowing down the heart beat rhythm,dilating vessels,inhabiting the activation of leukocyte,relieving the release of inflammatory mediator.It can also decrease the overload of Ca²⁺ etc.The main task of this research is to determine the protective effect of adenosine enrichment to ST.Thomas'Hosptialâ…¡cardioplegia on ischemic immature myocardium under ischemia repertusion injury and to approach the possible mechanisms of this effect by using the isolated Langendorff perfusion model.Methods and materials21±2days old immature heathy rabbits were used for this study with no considering of gender.All animals were randomly divided into control group and test group.10 for each group.After anesthesia induction(10%ChloralHydrate,intraperitoneal injection) and heparinization(heparin-sodium injection 500U for each rabbit),hearts were excised rapidly,rinsed thoroughly in chilled 4℃Krebs-Henseleit buffer(K-H buffer),connecting the aortic cannulation to the isolated Langendorff perfusion model,then perfused under a constant perfusion pressure of 60mmHg,With 37℃oxygenated K-H buffer.After 15mins of equilibration,Isolated working rabbit hearts were perfused with cardioplegia then subjected to 30 min of hypothermic(4℃) cardioplegic arrest and 90 min of normothermic(37℃) reperfusion.The test group (group B) received ST.Thomas'Hosptialâ…¡cardioplegia with adenosine(2mmol/L) enrichment and the control group(group A) was treated with ST.Thomas'Hosptialâ…¡cardioplegia.All these hearts received 30 mins of global ischemia and reperfused with 37℃K-H solusion until 90mins.Part of left ventricular myocardium were fixed in 10%formaldehyde for 48hrs.and then dehydrated,embeded in paraffin.Part of myocardium samples were fixed in 3.5%Pentanedial solusion.the coronary sinus flow (CF) of pre-ischemia and 30min,s 60min,s 90min,s after reperfusion were record,creatine kinase(CK) and lactate dehydrogenase(LDH) were measured by using the automatic biochemistries' detecting instrument.The Apoptotic index was calculated by using the tunnel method,the myocardial ultrastructure was studied under electron microscope.Results1,change of CF:compared with control group,The CF amount of propotional time spot was significant rised in test group(P＜0.05).2,change of myocardial enzyme leakig:compared with control group,the decrease of CK and LDH leaking in correspond time spot is significant(P＜0.05).3,change of apoptotic index(AI):compared with control group,apoptotic index is much lower(P＜0.05).4,change of ultrastructure:compared with control group,the change of ultrastructure is less obvious(P＜0.05).ConclusionAs a valuable addition to hypothermic cardioplegia,adenosine can protect myocardium from IRI(Ischemia-reperfusion injury)by increasing postischemiareperfusion coronory flow,allivating myocardial enzymes' leaking and cellular apoptosis.It can also relieve the change of myocardial ultrastructure causing by IRI and produce better protection for the myocardium of immature rabbit hearts.