| Background： Myocardial ischemia (myocardial ischemia) is a commonclinical pathological processes, it often caused by coronary heart disease due tocoronary artery stenosis or occlusion. When the supply of myocardial blood flow isreduced, cells reduce the intake of oxygen from the blood, the aerobic metabolism ofmyocardial cells decrease, ATP production decreased, it would not meet the needs ofthe body’s metabolism, while metabolic waste can not be effectively removed,causing tissue acidosis, calcium overload, ROS accumulation, and leading tomyocardial cell damage, cardiac dysfunction.Mitochondrial can generate ATP through oxidative phosphorylation, it is themain place of energy produced by eukaryotic cells, mitochondrial damage is deemedas the direct factor caused by cell aging, oxidative stress, apoptosis. Therefore,resistance to myocardial ischemia and hypoxia injury and preventing themitochondrial dysfunction may be an effective therapeutic strategy. MitochondrialATP-sensitive potassium channel (mitoK-ATP) exists in a wide range of the innermitochondrial membrane, As it is regulated by intracellular ATP concentration, whenthe intracellular ATP concentration was significantly reduced, it would result inopening the channel. Based on physiological functions of mitoK-ATP channel, wespeculated that opening mitoK-ATP channel may play a cardioprotective effect asincreasing cell efficiency of oxidative phosphorylation during ischemia and hypoxiaconditions, reducing oxidative stress and myocardial apoptosis through protecting thestructural integrity of mitochondria and maintaining mitochondrial function.In this study, we simulate clinical myocardial ischemia caused by coronary heartdisease leading to coronary artery stenosis or occlusion by giving isoproterenol andestablishing the myocardial ischemia injury model. We explore the role of mitoK-ATPchannel in myocardial ischemia injury in rats through using the method of histology and molecular biology.Methods：The clean male Wistar rats (200g±20g) were divided into fourgroups randomly, namely the control group (Control group), myocardial ischemiainjury group (ISO group), mitoK-ATP channel open group (Nic group) andmitoK-ATP channel blocker group (5-HD group). Control group: Using the equaldose of saline instead of the drugs. ISO group: intraperitoneal injection of ISO2ml/day (2ml:1mg). Nic group: intraperitoneal injection of ISO2ml/day (2ml:1mg), andintravenous injection nicorandil1.5mg/kg/day1h later.5-HD group:intraperitoneal injection of ISO2ml/day (2ml:1mg), intravenous injection nicorandil1.5mg/kg/day and intramuscularly5-HD,5mg/kg/day1h later. Each group ofanimals were reared in a clean condition for three days. In the fourth day, anesthesiaand collect specimens. TTC staining was applied to detect the extent of heart damageSpecimens; HE staining was used to observe the histological structure; TUNEL wasused to detect cell apoptosis. The expression of Kir6.2and Nitrotyrosine weredetected by using Western Blot; immunohistochemical assay was applied to detect theexpression of Kir6.2, Nitrotyrosine and Caspase-3.Results：TTC staining results was observed by the naked eye, can be visiblyseen ISO group, Nic group and5-HD group were appeared pale infarct area, butControl group did not show such situation. Statistical analysis of ISO groupmyocardial infarct revealed cover an area of (%):33.18±6.35, Nic group openingmitoK-ATP channel, myocardial infarct area was:15.18±2.55, significantly lowerthan the ISO group(P＜0.001).5-HD group blocking mitoK-ATP channel opening,myocardial infarct was:28.29±4.52, higher than the Nic group(P＜0.001). HEstaining was show that, the cell structure and cell morphology of Control group werenormal. ISO group showed myocardial cell edema and a large area of myocardialnecrosis. Nic group myocardial cell injury was significantly reduced compared withISO group, and necrosis was relatively limited. Myocardial tissue injury of5-HDgroup was damaged severly. TUNEL results showed no positive cells in the control group, the number of apoptotic cells increased significantly in ISO group, afteropening mitoK-ATP channel, the number of apoptotic cell was significantly reduced.Inhibit mitoK-ATP channel opening of5-HD group, the number of apoptotic cells wassignificantly increased. Immunohistochemistry and Western Blot detection Kir6.2expression of the heart tissue, in the Control group and5-HD group, the expressionlevel of Kir6.2was relatively low, ISO group was slightly higher than the Controlgroup expression, Nic group was much higher than the other three groups.Immunohistochemistry and Western Blot detected the expression of Nitrotyrosine, theresult showed that the expression of Nitrotyrosine in Control group was very low. ISOgroup expression increased significantly, Nic group Nitrotyrosine expression wassignificantly lower than ISO group, the Nitrotyrosine expression of5-HD group wassignificantly higher than Nic group. Immunohistochemical detected the expression ofactivated Caspase-3. It revealed that in Control group actived Caspase-3was negative.Stronger expression of activated Caspase-3was found in ISO group, Nic groupshowed a very low expression level of activated Caspase-3, the expression level of5-HD group was higher than Nic group.Conclusion：In this study, the preparation of the myocardial ischemia modelof rats administered by isoproterenol is successfully prepared, proving that openingmitoK-ATP channels plays an important role in protecting heart from myocardialischemia injury. It clarifies the mechanism involved is that by reducing theaccumulation of ROS in the organization in order to reduce cellular oxidative stressinjury, and reduce the apoptosis, and thus playing a cardioprotective effect role. |
PDF Full Text Request