| Objective: Myocardial ischemia(MI)is a pathological state.It is coronary artery stenosis and other causes of heart that reduce heart's blood perfusion,which will inevitably lead to inadequate blood and oxygen supply and clear reduction of metabolite.At present,as soon as possible to restore the blood supply,ischemic myocardium-reperfusion therapy,which is a method we generally adopted.However,reperfusion therapy can improve ischemia and hypoxia and rescue dying,at the same time,it can also cause myocardial ischemia reperfusion injury(MIRI).Now,exploring the mechanism of MIRI and seeking to avoid or mitigate the method has become a hot topic in the field of cardiovascular research.ATP-sensitive potassium channels(KATPC)opener,has showed obvious effect on heart protection in the process of prevention and treatment of MIRI.In this study,we made the rat myocardial ischemia-reperfusion(I/R)animal model at first,and chose a representative of a cardiac non-selective KATPC opener-nicorandil to intervene before surgery,Through the survey,we observe if nicorandil can reduce the reperfusion injury or not,and to further explore its influences of anti-oxidative stress and reducing inflammation,which will provide a new theoretical basis and treatment considerations in the clinical applications of MIRI.Methods:48 healthy adult male Sprague Dawley rats were randomized into three groups: Sham group(sham,n=16)Control group(I/R,n=16)Experimental group(nic,n=16).Nic group was given nicorandil 1mg/(kg.d),by intravenous injection,repeated dosing interval of once every 24 hours,for 1 week;however,Sham group,I/R group were given normal saline in the same way.Half an hour before surgery,Nic group was given additional day dose again,Sham group,I/R group were given normal saline.During the surgery,we operated thoracotomy,threaded line under left anterior descending coronary artery(LAD)without ligation in Sham group,and ligated the line for 30 minutes and then released it for 120 minutes in I/R group and Nic group.Standards of a successful I/R model are as follows: Ischemic left ventricular anterior wall turn to be dark(purple or blue-violet)and lead II synchronous ECG showed ST segment elevation no less than 0.2m V,or T wave upright,QRS wave group higher or widening range during ischemia.There were coronary blood flow restoration,the color recovery of ischemic myocardium area,tall T wave rapid decline,elevated ST segment back down more than 50% after loosing the ligature.After operation,each group was blood,the level of creatine kinase isoenzyme(CK-MB)in Serum was discerned.We used enzyme-linked immunosorbent assay(ELISA)method to measure tumor necrosis factor-a(TNF-a),interleukin-6(IL-6),xanthine oxidase to detect the activity of cardiac total superoxide dismutase(T-SOD)and thiobarbituric acid(TBA)method to detect malondialdehyde(MDA)level;double staining method(2,3,5-triphenyl tetrazolium chloride(TTC)and Evans blue)to measured the myocardial infarct size.By this way,visually normal cardiac area can be stained into blue,but gray for myocardial infarction region and light red for the ischemic myocardial tissue.The myocardial infarct size was expressed as the AN/AR,namely the percentage of the total infarct area divided by total area at risk(the sum of infarct region and ischemic area).Risk area is calculated: AR/ALV,where LV represents the area of left ventricle.Computer analysis software is applicated in each group AN/AR and AR/ALV.The SPSS 13.0 software is applied for all experimental statistical analysis,measurement statistical indicators is examined in line with normality and homogeneity of variance,All indicators are expressed as mean±standard deviation,T test was used to compare groups between two groups.Many groups of the completely random design were compared by ANOVA(one-way ANOVA),or rank sum test(Kruskal-WAllis H),The comparison of each two groups was analyzed by LSD.We took ?=0.05 as statistic significant level.Results:1 Electrocardiogram(ECG)lead II: The ECG of rats before surgery were normal.The ECG of Sham group showed no change;in I/R group and Nic group,after LAD ligation in rats,ECG showed large abnormal QRS,ST segment elevation arched shape,T wave elevation.When reperfusion,there were T wave down quickly,ST segment down more than 50%,I/R group had one rat dead because of ventricular fibrillation,one rat occurred a short ventricular tachycardia in Nic group,five rats in I/R group and three in Nic group appeared atrioventricular block,part stayed pathological Q waves.2 The CK-MB levels of Sham group,I/R group,Nic group were:(19.69±4.55)IU/L,(83.52±6.63)IU/L,(75.76±5.25)IU/L,compared with Sham group,the CK-MB of I/R group and Nic group elevated(P<0.01);elevated CK-MB level in Nic group is less than I/R group(P<0.05).3 The TNF-?levels of Sham group,I/R group,Nic group were:(28.92±15.72)pg/ml,(180.56±22.97)pg/ml,(122.18±19.49)pg/ml,compared with Sham group,the TNF-?of I/R group and Nic group increased(P<0.01);increased TNF-?in I/R group significantly more than that in Nic group(P<0.01).4 The IL-6 levels of three groups were respectively:(63.20±7.90)pg/ml,(164.44±9.29)pg/ml,(120.64±8.11)pg/ml,the IL-6 in I/R group and Nic group were higher than that in Sham group(P<0.01);the increase of IL-6 in I/R group was more obvious than in Nic group(P <0.01).5 The T-SOD levels of three groups were respectively:(134.50±8.04)U/mgprot,(94.45±6.71)U/mgprot,(112.27±5.17)U/mgprot,compared with Sham group,the T-SOD of I/R group and Nic group decreased(P<0.01);the T-SOD level in I/R group decreased significantly compared with that in Nic group(P<0.01).6 The MDA were respectively in three groups:(2.18±0.52)nmol/mgprot,(5.47±0.38)nmol/mgprot,(3.80±0.52)nmol/mgprot,compared with Sham group,the MDA of I/R group and Nic group increased(P<0.01);the MDA in I/R group was significantly higher than that in Nic group(P<0.05).7 For I/R group and Nic group,the percentages of AR/ALV were respectively:(37.77±4.42)%,(37.09±3.36)%,the difference was not significant in statistics(P>0.05),showing the risk of myocardial ischemia was similar.For infarct size,AN/AR,the percentages in I/R group and Nic group were(66.52±6.55)% and(48.64±7.86)%,respectively.Compared with I/R group,the infarct size in Nic group reduced(P <0.01).Conclusion:1 Nicorandil pretreatment can effectively remove oxygen free radicals in rats,anti-lipid peroxidation,decrease MDA levels,increase T-SOD levels,enhance the body's anti-oxidative stress ability,protect myocardium.2 Nicorandil pretreatment can suppress inflammation in rats,reduce inflammatory cytokine TNF-? and IL-6's production and release,reduce the body's inflammatory injury,protect myocardium.3 Nicorandil pretreatment can reduce CK-MB increaced rate in rats,reduce myocardial infarct size. |
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