Dynamic Change Of Nitric Oxide Synthetase(NOS)and Its Gene Expression During Myocardial Ischemia And Reperfusion

BACKGROUND: Cardiac Surgery has been greatly developed since first heart operation was done in condition of cardiac arrest by cardiopulmonary bypass in 1953. In that normal coronary circulation is occluded,myocardium is suffered ischemia and anoxia result in myocardial injury and necrosis during cardiac surgery.Myocardial injury is associated with lots of postoperative mortality and complications. To date myocardial protection theory has been constantly evolved in clinical,subcellular and molecular level since Melrose used cardioplegic solution in 1955.Clinical myocardial protection research is emphasized in improvement of cardioplegic composition and delivery method.Although myocardium is protected in ischemic phase,it is found that restoration of blood flow may carry along an injurious component which counteract the beneficial effects of reperfusion.This pererfusion attact phenomenon may manifest as myocardial edema,decreased utilization ability of oxygen or matrix,depletion of high energy phosphate and glycogen,intracellular deposition of calcium salt,mitochondrial injury,myocardial constractile dysfunction and change of ventricular complience.Since this phenomenon is appeared few minutes after restoration of blood flow,it is termed ischernic reperfusion injury(IRI).Now there are many evidences 5 that neutrophil and oxygen radical are important factors which lead to PRI.Coronary vascular endothelium is a major targit attacted by neutrophil and oxygen radcaLAnd it is found that coronary vascular endothelium is an original source of oxygen radicaljn this knowledge,it is as same important to protect coronary vascular endothelium as protect myocardium. In 1987 it was first time proved that the major active component of endothelial derived relaxing factor was nitric oxide(NO).ln the vascular system,NO accounts for vasorrelaxion as well as inhibition of platelet and neutrophil adhension,aggregation and activation.The role of NO in myocardial ischemia reperfusion injury has been studied intensively,but it is still unclear whether NO is protective or injurious to the reperfused heart.And the research results are often contrary.To exactly explain these differences is not easy. Maybe the disturbance in expression of NOS subtype and activity attributes to these contrasting results. Therefore, the aim of the present study was to reveal the dynamic change of NOS activity, NO content and eNOSI1NOS gene expression during myocardial ischernia and reperfusion. The main tasks of this research are: (1) TO estabilish in vivo heart ischemia reperfusion animal model.(2)To detect the dynamic change of NOS activity and NO content at different point during myocardial ischemia and reperfusion; (3) To detect the dynamic change of eNOS/iNOS gene expression via RT-PCR. MATERIALS AND METHODS In vivo myocardial ischemic reperfusion animal model was made via ligation of coronary atery left anterior descending branch of NewZealand rabbit. Animal models were divided into 6 groups:group I was normal sham operational myocardium(n~5), 6 group 2 underwent myocardial ischemia for 30 min(n=5), group 3 underwent myocardial ischemia for 60 min(n~5), group 4 underwent myocardial isc...