| Objective: This experiment aim at using nicorandil preconditioning to observe the effect of nicorandil on reperfusion arrhythmia on rats.Meanwhile we will discusse the possible mechanism on experimenl results,and explore a new way of the clinical application of nicorandil.Methods: We selected forty-five healthy adult Wistar rats randomly and divided into three groups: sham group(Sham group),ischemia reperfusion group(I/R group)and nicorandil group(Nic group).The left anterior descending(LAD)coronary artery was roundby the operative line after thoracotomy without ligation in Sham group.LAD was ligated for 30 minutes reversibly and reperfused for 120 min in I/R group and Nic group.We gave nicordil The rats in Nic group received nicorandil pumped into the vein continuously until reperfusion for 120 minutes.We recorded the ECG separately when LAD ligated for 30 minutes and reperfused for 120 minutes,and the incidence of arrhythmia,arrhythmia score,ventricular tachycardia durations(VT durations).We Classified the arrhythmia types according to Lambeth Convention.The Curtis-Walker score was used to evaluate arrhythmia score.Among which the VT durations means the mean durations of ventricular tachycardia in each group.Then we counted the incidence of arrhythmia in each group before and after reperfusion,and compare the above indexs within each group.The rats were killed after reperfusion,and the blood was taken from the chambers of the heart quickly.Then we tested the serum creatine kinase isoenzymes(CK-MB)and lactate(Lactate).The myocardial infarction was double-stained with Evans Blue&TTC.We used Image Analysis software to analyze the risk and infarct area.At last we observed the myocardial ultrastructure in each group with transmission electron microscope.Results: In the course of the experiment,2 rats in the I/R group and 1 rat in the Nic group were dead and eliminated because of poor tolerance or misoperation during operation.In the end,42 rats were operated successfully,15 in Sham group,13 in I / R group,and 14 in Nic group.1.There was no significant difference in the incidence of arrhythmia in each group after ischemia for 30 minutes(P>0.05).The arrhythmia score of the three groups was similar(P>0.05).The VT durations of the three groups before reperfusion was similar(P>0.05).2.The incidence of arrhythmia in I/R group was higher than that in Sham group after reperfusion 120 minutes(P<0.01).The arrhythmia scores in the I/R group after reperfusion were higher than those in the Sham group(P<0.01、P<0.05).The arrhythmia score of Nic group was lower than that of I/R group(P<0.05).The VT durations in I/R and Nic group was significantly longer than that in Sham group(P<0.01、P<0.01).However,the durations of VT in I/R group was similar to that in the Nic group,and there was no significant difference between these two groups(P>0.05).3.Compared with Sham group,the CK-MB level in I/R and Nic group was significantly higher(P<0.01,P<0.01).The difference between Nic group and I / R group was statistically significantly(P<0.01).4.Compared with Sham group,the level of lactate in I/R group and Nic group increased significantly(P<0.01).Compared with I/R group,the lactate level in Nic group decreased significantly(P<0.01).5.There was significant difference in infarct area IS/AAR between I/R group and Nic group(P<0.01).There was no significant difference in risk area AAR/ALV between I/R group and Nic group(P>0.05).6.Myocardial ultrastructure: The myocardial and mitochondrial structure in Sham group was normal;The myocardial and mitochondrial structure in I/R group was damaged obviously;The myocardial and mitochondrial structure in Nic group was damaged slightly.Conclusions:1.Nicorandil preconditioning before myocardial ischemia-reperfusion can improve the malignancy of reperfusion arrhythmias,decrease the incidence,arrhythmia score,and the mean duration of ventricular tachycardia;2.Nicorandil can not only reduce the infarct size and the damage of myocardial ultrastructure,but also improve the local acidosis.It has good protective effect on reperfusion myocardium.3.The mechanism of nicorandil in improving arrhythmias may be related to the reduction of myocardial acidosis,the protection of myocardial ultrastructure and the reduction of ischemia-reperfusion injury. |
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