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AIM: To investigate the role of Ca2+ - activated, delayed - rectifier and ATP sensitive K+ channel (KCa, Kdr, KATP) in airway hyperresponsiveness of asthmatic guinea pigs. METHODS: The method of recording the tone of isolated trachea rings was performed, and the changes of dose-response curves of trachea rings to histamine caused by different K+ channel blockade were investigated. RESULTS: (1) After inhibition of KCa, by tetraethylammonium (TEA) , the dose - response curve of trachea rings to histamine did not change in control group, while the maximal contraction of trachea rings to 10-4 mol/L and 10-3 mol/L histamine decreased significantly ( P
RESUMO
AIM: To investigate the effects of the selective mitochondrial ATP-sensitive K+ channels opener diazoxide on mitochondrial respiratory function and enzyme activity in isolated rat myocardium under ischemia/reperfusion.METHODS: Observation was made on rat hearts perfused with Langendorff apparatus.72 Sprague-Dawley(SD) rats were randomly divided into 4 groups: normal group(NOR),ischemia reperfusion(IR),diazoxide group(DIA) and 5-hydroxydecanoate(5-HD) antagonized diazoxide group(5HD-DIA).Hearts isolated from SD rats were mounted on a Langendorff apparatus and started with a 20 min perfusion for equilibration.NOR went on perfusion for another 100 min after equilibration.IR underwent 40 min global ischemia and followed by 30 min reperfusion after 30 min stabilization.DIA was administered with K-H solution containing diazoxide at concentration of 50 ?mol/L for 10 min before ischemia and reperfusion.5HD-DIA was infused with 100 ?mol/L 5-HD(a specific mitochondrial ATP sensitive K+ channel blocker) and the same procedure was carried out as DIA group.Hearts were taken down to extract mitochondrial at the end-equation,before ischemia and at the end-reperfusion for determination of mitochondrial respiratory function and the enzyme activity of mitochondria.RESULTS: At the end of reperfusion,mitochondrial respiratory function(mitochondrial respiratory control rate,P/O ratio and state 3 respiration) and mitochondrial enzyme activity(NADH oxidase,succinate oxidase and cytochrome C oxidase) in DIA group were better than those in IR group and 5HD-DIA group(P0.05).CONCLUSION: Preconditioning with mitochondrial ATP sensitive potassium channel opener,diazoxide,protects rat heart mitochondria against ischemia-reperfusion injury.The mechanisms are involved in the safeguarding of respiratory function and activity of enzymes of respiratory chain.