Nicorandil Plays A Role In Protecting Myocardial When Isoprenaline Induced Rat Acute Myocardial Damage

Background and purpose:Isoprenaline (ISO) as a kind of nonselective betareceptor agonist can enhance myocardial contraction,increase cardiac conductionsystem of the conduction velocity and speed up the heart rate.High dose of ISO canmake the myocardial oxygen consumption has increased dramatically and finally leadto acute myocardial damage.Myocardial cell necrosis, myocardial interstitial fibroustissue hyperplasia, connective tissue accumulation cause cardiac compliance isreduced, systolic and diastolic function is inhibited, so long-term can cause chronicheart failure.We found ATP enzyme formation decreases in the mitochondrial fromseparated human and animal failure heart, ATP is the main product of electrontransport chain,it shows that the failure of the heart mitochondrial energy generationreduce may relevant with respiratory chain damage and radical scavenging proteindamage.Increases in mitochondrial generated ROS result from mitochondrial dysfunctionor imbalance of antioxidant homeostasis,and have been implicated in contributing toaging and age-related diseases. Lipid oxidation play an important role incardiovascular disease atheromatous plaque formation of the initial stage. Nicorandil isa kind of mitochondrial ATP-sensitive potassium channels open agent(mitokATP),itcan protection the myocardial and maintain the normal function of the heart. KATPmaintain cardiac function when it is interfered can make the heart to ischemia andmetabolic inhibition of the sloe response,and suppress myocardial. Nicorandil canrestrain myocardial apoptosis caused by the oxidative stress and low oxygen,andprevent myocardial remodeling. This experiment through use the ISO induced rat acutemyocardial injury, research nicorandil is how protect myocardial cell function and prevent myocardial damage,in order to provide new drug effect targets for clinicaltreatment.Experimental methods: Healthy male wistar rats were randomly divided intothree groups:blank control,isoproterenol group (ISO group) and nicorandil treatmentgroup(Nic group). Give ISO group intraperitoneal injection ISO200mg/kg,2times/day, succession two days,making rat acute myocardial damage model. Nicgroup give the same way but need give nicorandil1mg/kg tail vein injectiong aftereach time after the injection in ISO1hour.Blank control give the same dosephysiological saline celiac injection. After using drug three days,we randomly extractrats and do electrocardiogram (ECG) analysis, at the same time analyze myocardialdamage markers and HE staining in order to judgment model preparation and damage.After three weeks,we continue Masson staining, immunofluorescence technicaldetection ɑ smooth muscle actin (ɑ-SAM) and immunohistochemical technicaldetection nitro-tyrosine generation.Statistical analysis：Data is reported as means±SD. Comparisons were madebetween different treatment groups using ANOVA, followed by the Dunnett post hoctest for differences. Data for percent changes were analyzed using the Kruskal-WallisH-test. A value of P <0.05was considered significant.Results：1、The rate of survivors in control group rats is100%, ISO group is65%,Nic group is85%. After3days three groups rats’ECG altered obviously, ISOgroup ECG showed obvious ST-T change than the control group, the performance isST segment move up greater than0.2mv, T wave flat. Nic group also chang but notobvious than ISO group. The above results suggest that intraperitoneal injection ISOmay duplicate successfully rat acute myocardial damage model model.2、Histopathological examination of the cardiac tissues: HE showed that in thecontrol group the myocardial fibers were arranged regularly with clear striations.NOapparent degeneration or necrosis was observed. Histological sections of theisoproterenol treated hearts showed that widespread myocardial cellnecrosis,hypertrophy, and abundant fibroblastic hyperplasia with capillary dilatationand leukocyte infiltration. Nic group significantly inhibited inflammatory reaction andthe myocardial cell necrosis and fibrosis. 3、Serum enzymology examination: CK and LDH in the ISO group wereobviously higher than the control group, the difference was statistically significant (p＜0.05). CK and LDH in the Nic group were obviously lower than the ISO group andthe control, the difference was statistically significant (p＜0.05). The above resultssuggest that ISO can induced successfully induced rat acute myocardial damage andnicorandil can protect myocardial form injury.4、Masson stain: The control group shows that myocardial cell is primary andno obvious myocardial interstitial and collagen composition. The ISO group showsthat there were a large number of collagen formation, myocardial occur obviouslyfibrosis,and only a small amount of myocardial cells are present. Collagen fiber in theNic group hyperplasia degree is significantly reduce than ISO group, and myocardialcell were destroyed also obviously reduced.5、Immunofluorescence technical detection ɑ smooth muscle actin (ɑ-SAM）：The control group shows that ɑ-SAM of smooth muscle cells in blood vessel wall isnegative through TRITC dyeing, and the performance of the vessel wall is a largenumber of red fluorescence. Then Nic group is not obvious than ISO group.6、Immunohistochemical method: ISO group shows that myocardial tissue cellarrangement is visible disorder, claybank particles in the cell cytoplasm can be seen.But control group myocardial cell is in alignment, staining in the cytoplasm isnegative, the results in Nic group showed significantly reduce than ISO group.Conclusions：When rats occur acute myocardial injury object the appropriate dose ATPsensitive potassium channels openers(Nicorandil) can play a protective myocardialrole. The main pathways for the way by reducing the nitro tyrosine, improvemitochondrial MnSOD2tyrosine kinase activity,reduce oxidative stress aftermyocardial ischemia hypoxia on myocardial damage.