纳他卡林对鼠脑线粒体ATP敏感性钾通道的开放作用

目的 探讨纳他卡林对脑线粒体ATP敏感性钾通道的影响.方法急性分离大鼠脑线粒体,采用Clark氧电极法测定纳他卡林对线粒体耗氧速率的影响;采用紫外分光光度法测定纳他卡林对线粒体悬液在540 nm处的吸光值的影响,用以监测线粒体基质容积的变化.结果纳他卡林可使脑线粒体的耗氧速率增加(7.58±2.76)%(P＜ 0.05...     

线粒体ATP敏感性钾通道与心肌保护的研究进展

缺血预处理对心肌的保护作用强大,但其机制复杂,涉及许多信号转导途径。目前认为线粒体ATP敏感性钾通道是其终末效应器。是细胞的一种重要离子通道,其结构复杂,功能多样,在细胞的生理、病理生理过程中起着重要作用。线粒体ATP敏感性钾通道的心肌保护机制主要涉及减轻缺血细胞钙超载,减轻自由基损伤,减少细胞凋亡及减轻远期心室重构。就线粒体ATP敏感性钾通道的结构及其心肌保护机制作一综述。     

线粒体ATP敏感性钾通道开放剂二氮嗪对大鼠缺血心肌细胞的保护作用

目的评价线粒体ATP敏感性钾通道(mitoKATP)开放剂二氮嗪对缺血损伤的心肌细胞超微结构和死亡率的影响。方法选用Wistar大鼠30只,随机分为正常对照组、心肌细胞损伤模型组(皮下注射异丙肾上腺素5mg/kg)和二氮嗪20mg/kg组。24h后处死动物,观察心肌细胞超微结构的改变。结果异丙肾上腺素皮下注射可以引起心肌细胞超微结构明显受损,预先给予二氮嗪口服可以减轻超微结构的损伤。二氮嗪10～100μmol/L可以降低缺血心肌细胞的死亡率,与对照组比较差异有统计学意义(P<0.01)。结论二氮嗪对缺血损伤的心肌细胞具有保护作用。     

ATP敏感性钾通道与心肌保护

在生理状态下，ＡＴＰ敏感性钾通道处于失活状态，急性心肌缺血及心肌肥厚时该通道被激活，这可能是一种重要的心肌内源性保护机制。     

线粒体ATP敏感性钾通道与缺血预处理的研究进展

1986年Murry等提出了缺血预处理（ischemia preconditioning,IPC）的概念。预处理的心肌保护范围广泛,作用强大,可以显著缩小梗死心肌面积,减少缺血／再灌注后心律失常的发生,明显改善心脏功能。Gross等提出心肌细胞的ATP敏感性钾通道（ATP—sensitive potassium channel,KATP）参与了IPC的心肌保护作用,KATP通道是一组将细胞膜电活动与细胞代谢联系在一起的重要通道。     

他汀预处理的心肌保护作用与ATP敏感性钾通道

急性冠脉综合征患者早期他汀治疗的疗效与其非降脂作用有关。他汀具有多种非降脂作用,新近研究发现其能作用于心肌产生保护作用。有多个资料显示,他汀预处理有明确的心肌保护作用,如改善微血管的通透性,抑制炎症反应,减轻心肌细胞结构损伤和缩小心肌梗死的范围。ATP敏感性钾通道(KATP)已被公认为是缺血预处理的重要环节。心肌KATP有两个结构、功能不同的位点,即细胞膜KATP(sarcolKATP)和线粒体膜KATP(mitoKATP),二者分别以不同的机制在缺血预处理或药物预处理中发挥作用。有资料证实,KATP途径是他汀预处理的重要机制,其中mitoKATP可能发挥着重要作用,而他汀预处理与sarcolKATP的关系尚未见报道。     

线粒体ATP敏感性钾通道与心肌缺血预适应

ATP敏感性钾通道 (KATP)是缺血预适应的重要环节 ,但KATP介导缺血预适应的作用位点是在心肌细胞膜还是在线粒体尚有争议。本文就线粒体KATP的结构 ,功能和在缺血预适应中的作用与机制作一综述。     

肺动脉平滑肌细胞ATP敏感性钾通道研究进展

ATP敏感性钾通道(K_(ATP))是将细胞代谢与细胞膜电活动耦联在一起从而影响细胞功能的重要通道。K_(ATP)是由磺酰脲受体(sulfonylurea receptor,SUR)和内向整流钾通道亚单位(Kir6．x)组成的异源八聚体,其中肺动脉平滑肌细胞(pulmonary artery smooth muscle cell,PASMC)的K_(ATP)主要由SUR2B和Kir6．1形成。在某些病理条件下,K_(ATP)参与了肺血管张力的调节。K_(ATP)活性受多种因素的调控,胞内二磷酸核苷酸(NDPs)、钾通道开放剂(potassium channel opner,KCOs)等可激活该通道,而ATP和硫脲类药物则特异性抑制该通道的开放。对PASMC中K_(ATP)通道的结构及其调节机制的了解,为相关疾病的治疗与预防开辟了一条新的途径。     

ATP敏感性钾通道开放剂治疗脑缺血的前景

钾通道开放剂是近期开发的新型心血管类药物 ,也是医学、药学领域继钙拮抗剂后又一研究热点。ＡＴＰ敏感性钾通道 (ＡＴＰ ｓｅｎｓｉｔｉｖｅＫ+ ｃｈａｎｎｅｌ,ＫＡＴＰ)开放剂是目前研究最多、应用最广的钾通道开放剂。从 80年代中期开始对其进行研究至今 ,已取得了显著进展。至今有 18个化合物进入临床实验阶段 ,10 0多个化合物在临床前研究阶段并评价出各自的药理学与实验治疗学特征。以血管平滑肌和胰腺 β细胞ＫＡＴＰ为靶标 ,开发出一系列激动剂和拮抗剂 ,已成功应用于抗高血压、抗心肌缺血和治疗非胰岛素依赖型糖尿病等[1] 。近年…     

刺五加皂甙B对心肌线粒体ATP敏感性钾通道的作用

研究刺五加皂甙B(Sb)对心肌线粒体ATP敏感性钾通道 (mitoKATP)的作用。用酶解法获取兔心室肌细胞 ,分为对照组、0 .1mmol/LSb组、0 .5mmol/LSb组、1mmol/LSb组、格列本脲组和格列本脲 +1mmol/LSb组。用罗丹明 (Rhodamine 12 3)染色 ,激光扫描共聚焦显微镜 (多光子模式 )观察线粒体荧光强度变化。结果 :①观察 15min对照组线粒体荧光强度无明显变化。② 0 .1,0 .5和 1mmol/LSb组均可见用药后线粒体荧光强度明显增加 ,分别增加 10 .3%± 6 .78%、18.4 %± 5 .5 1%和 2 4 .1%± 7.6 4 % ,荧光强度的增加以前 5min为主。③ 3μmol/L格列本脲不影响线粒体荧光强度 ,但可以阻断Sb对线粒体荧光强度的作用。结论 :Sb对mitoKATP有开放作用。     

Involvement of ATP-sensitive potassium channels in preconditioning protection

Summary Single or multiple brief periods of ischemia (preconditioning, PC) have been shown to protect the myocardium from infarction during a subsequent more prolonged ischemic insult. To test the hypothesis that opening of ATP-sensitive potassium channels (K_ATP) is involved in this mechanism, either bimakalim, a K_ATP channel opener, or glibenclamide, a K_ATP channel blocker, were administered to mimic or to block preconditioning protection in barbital-anesthetized pigs. PC was elicited by a single period of 10 min left anterior descending coronary artery (LADCA) occlusion followed by 15 min of reperfusion before the LADCA was reoccluded for 60 min. Instead of PC, bimakalim infusion was started 15 min before the 60 min LADCA occlusion (TCO) and stopped with the onset of ischemia. Glibenclamide was administered either for 10 min prior to the PC protocol, before bimakakim infusion, or before TCO. Regional wall function was quantified with ultrasonic crystals aligned to measure wall thickening (%WT). At the end of the protocol, infarct size was determined by incubating myocardium with p-nitrobluetetrazolium.In seven preconditioned pigs, infarct size was 9.9±5.1% of the risk region compared with 65.9±6.0% in the seven control pigs subjected to 60 min of ischemia only (p<0.001). In seven pigs treated with bimakalim, infarct size was reduced to 35.3±6.6 (p<0.05 vs. controls). Blocking ATP-sensitive potassium channels with glibenclamide prior to PC abolished its protective effect (infarct size, 62.2±4.5%;p<0.001 vs. PC alone). Glibenclamide also antagonized the protective effect of bimakalim (infarct size, 55.2±4.0%), but did not affect infarct size, when solely administered prior to the prolonged ischemic period (62.2±4.3%). We conclude that in swine myocardium K_ATP channels are involved in the protective effect of ischemic preconditioning, since glibenclamide completely abolished the protective effect of preconditioning, while bimakalim could — at least in part — mimic it.Dedicated to Prof. Dr. H.-J. Langmann on the occassion of his 70th birthday.     

ATP敏感性钾通道与低氧性肺动脉高压

研究证明肺血管上存在ATP敏感性钾通道（KATP通道），该通道参与了膜静息电位和血管紧张性的调节。在低氧性诱导的肺动脉高压中，KATP通道参与了血管收缩和重构的病理过程。了解KATP通道的结构和其生物学特性，对认识低氧性肺动脉高压的形成机制和发展新的临床治疗手段有重要意义。     

ATP-sensitive potassium channels and myocardial preconditioning

The ATP-sensitive potassium channel (K_ATP) has been shown to serve an endogenous cardioprotective role in a number of experimental models of myocardial stunning and infarction. More importantly, a majority of evidence has also been obtained which suggests that the K_ATP channel may be intimately involved in both triggering and maintaining the cardioprotection afforded by the phenomenon of ischemic preconditioning particularly in large animal models such as dogs and pigs. Although the evidence for an involvement of K_ATP in ischemic pre-conditioning is equivocal in smaller animal species such as rabbits and rats, activation of this channel by K_ATP channel openers produces cardioprotection in all species studied. Whether this channel is an important mediator of ischemic preconditioning in all animal species including man and the mechanism by which this cardio-protective effect is obtained await further experimental studies. Nevertheless, the use of selective potassium channel openers to mimic preconditioning in selected clinical settings may be a desirable future therapeutic goal.     

Nicorandil inhibits oxidative stress-induced apoptosis in cardiac myocytes through activation of mitochondrial ATP-sensitive potassium channels and a nitrate-like effect

The anti-anginal drug nicorandil has been shown to inhibit apoptosis by activating mitochondrial ATP-sensitive potassium (K(ATP)) channels. The possible contribution of the nitrate moiety of this drug to its anti-apoptotic effect has now been investigated in neonatal rat ventricular myocytes subjected to oxidative stress. Exposure of cultured myocytes to 100 micromol/l hydrogen peroxide (H(2)O(2)) increased the number of nuclei stained by the terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling technique as well as induced internucleosomal DNA fragmentation, loss of mitochondrial membrane potential, cytochrome c release into the cytosol, and activation of caspases-3 and -9, all of which are characteristics of apoptosis. Pretreatment of cells with nicorandil (100 micromol/l) inhibited these effects of H(2)O(2). Both the mitochondrial K(ATP) channel antagonist 5-hydroxydecanoate (5-HD) and 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ), an inhibitor of soluble guanylyl cyclase, attenuated the anti-apoptotic effect of nicorandil in concentration-dependent manners. Coapplication of ODQ (10 micromol/l) and 5-HD (500 micromol/l) completely abolished nicorandil-induced cytoprotection. The effect of nicorandil was also reduced by an inhibitor of cGMP-dependent protein kinase (KT5823, 1 micromol/l). The nitric oxide donor (+/-)-S-nitroso-N-acetylpenicillamine (SNAP, 50 micromol/l) mimicked the protective effect of nicorandil in a manner sensitive to ODQ but not to 5-HD. A cell-permeable cGMP analog, 8-bromo-cGMP, also reduced H(2)O(2)-induced apoptosis. The inhibition of the H(2)O(2)-induced activation of caspase-3, but not that of caspase-9, by nicorandil in the presence of 5-HD or by SNAP was reversed by the addition of dithiothreitol to the enzyme assay. Nicorandil inhibits oxidative stress-induced apoptosis in cardiac myocytes through a nitric oxide/cGMP-dependent mechanism as well as by activating mitochondrial K(ATP) channels.     

对KATP通道介导缺血预适应心肌再灌注损伤的研究

目的探讨优降糖对KATP通道介导心肌缺血预适应作用的影响。方法将44只大鼠随机分为心肌缺血预适应组(IPC组)、优降糖组(GLI组)、优降糖 IPC组(G-P组)和对照组(C组)。心肌缺血预适应由3次10min缺血/10min再灌注组成。所有大鼠均接受30min缺血/60min再灌注。梗死范围由饱和曲利本蓝和红四氮唑蓝染色判定,并以坏死区占缺血区的百分率表示。Ⅱ导联记录心脏室性心律失常。结果IPC能显著缩小缺血/再灌注后的心肌梗死范围,且这种作用能被KATP通道阻滞剂优降糖完全取消。IPC可减少缺血/再灌注所致的室性心律失常的发生,但这种保护作用不能被优降糖所阻断。结论优降糖对KATP介导IPC的心肌保护作用有影响。     

Blockade of ATP-sensitive potassium channels by 5-hydroxydecanoate suppresses monophasic action potential shortening during regional myocardial ischemia

Summary We tested 5-hydroxydecanoate (5-HD), a specific blocker of ATP-sensitive potassium channels (IK.ATP), to determine if it mitigates electrophysiologic changes produced by regional myocardial ischemiain vivo. A sequence of 5-minute occlusion of the distal LAD and 30-minute reperfusion was repeated while recording the monophasic action potential (MAP) and bipolar electrogram (EG) from the epicardial center of the ischemic myocardium in anesthetized dogs. 5-HD (30 mg/kg, IV) or glibenclamide (0.15 or 0.3 mg/kg, IV) was administered before the third occlusion, and the data were compared to the second occlusion data. 5-HD did not affect baseline MAP duration at 90% and 50% repolarization (APD90, APD50) before LAD occlusion but suppressed occlusion-induced shortening of APD90 (16 ± 2% during the second occlusion vs. 5 ± 3% during the third occlusion, n=8, p<0.01) and APD50 (16 ± 3% vs. 10 ± 3%, n=8, p<0.05). Pretreatment with glibenclamide also suppressed occlusion-induced MAP shortening and eliminated an additional effect of 5-HD (n = 3). 5-HD did not affect the occlusion-induced increase in duration and activation time of EG. 5-HD, as well as glibenclamide, suppressed regional ischemia-induced MAP shortening, probably by blocking activation of IK.ATP, without affecting conduction delay. These differential effects of 5-HD on repolarization and conduction during the early phase of regional ischemia might have the potential to suppress reentrant ventricular arrhythmias.This study was supported in part by Mitsukoshi Prize of Medicine 1993 (Satoshi Ogawa, Toshihisa Miyazaki).     

Effect of repaglinide on cloned beta cell, cardiac and smooth muscle types of ATP-sensitive potassium channels

Aims/hypothesis. The carbamoylbenzoic acid derivative repaglinide is a potent short-acting insulin secretagogue that acts by closing ATP-sensitive potassium (K_ATP) channels in the plasma membrane of the pancreatic beta cell. In this paper we investigated the specificity of repaglinide for three types of cloned (K_ATP) channel composed of the inwardly rectifying potassium channel Kir6.2 and either the sulphonylurea receptor SUR1, SUR2A or SUR2B, corresponding to the beta cell, cardiac and either smooth muscle types of K_ATP channel, respectively. Methods. The action of the drug was studied by whole-cell current recordings of K_ATP channels expressed either in Xenopus oocytes or mammalian cells (HEK293). We also used inside-out macropatches excised from Xenopus oocytes for detailed analysis of repaglinide action. Results. The drug blocked all three types of K_ATP channel with similar potency, by interacting with a low-affinity site on the pore-forming subunit of the channel (Kir6.2: half-maximal inhibition 230 μmol/l) and with a high-affinity site on the regulatory subunit, the sulphonylurea receptor (SUR: half-maximal inhibition 2–8 nmol/l). There was no difference in potency between channels containing SUR1, SUR2A or SUR2B. MgADP potentiated the inhibitory effect of repaglinide on Kir6.2/SUR1 and (to a lesser extent) Kir6.2/SUR2B, but not on Kir6.2/SUR2A. Conclusion/interpretation. Repaglinide interacts with a site common to all three types of sulphonylurea receptor leading to inhibition of the K_ATP channel. The fact that MgADP potentiated this effect in the case of the beta cell, but not cardiac, type of channel could help explain why the drug shows no adverse cardiovascular side-effects in vivo. [Diabetologia (2001) 44: 747–756] Received: 13 December 2000 and in revised form: 14 February 2001     

三磷酸腺苷敏感性钾通道在心肌缺血预适应中的作用

采用结扎家兔左冠状动脉左室支复制心肌缺血预适应（ＩＰ）模型，研究三磷酸腺苷敏感性钾（ＫＡＴＰ）通道在ＩＰ中的作用。结果表明：ＩＰ能缩小梗塞面积和恢复再灌注期心脏功能；活化ＫＡＴＰ通道显著加强ＩＰ的作用，尤以恢复心功能为著；阻滞ＫＡＴＰ通道则抑制ＩＰ的作用。提示ＫＡＴＰ通道活化与ＩＰ作用有关。