心血管系统中的ATP敏感性钾通道

<正> 钾通道几乎存在于每一种细胞,种类繁多,功能复杂。近年来由于膜片钳制技术(patch-clamp)广泛应用,加之发现一些对一定类型钾通道有特异性阻滞作用的毒素、药物以及钾通道开放剂(potassium channel open-er,PCO)等,人们能在单个离子通道水平对复杂多样的钾通道进行分辨和区分,对通道蛋白进行分离、纯化、重组,使钾通道研究取得了长足进展,成为一个非常活跃的研究领     

血管平滑肌ATP敏感性钾通道研究进展

ATP敏感性钾通道 (KATP)广泛存在于各类细胞和组织中 ,是药物作用的重要靶点。KATP是由内向整流钾通道Kir和磺酰脲类受体SUR亚基组成。与血管舒缩特性密切相关的是SUR2B/Kir6 1,电导值小 ,对ATP的抑制作用不敏感 ,需要有NDP才能被开放 ,故这类血管平滑肌KATP又被称为NDP依赖性钾通道。内源性和外源性的很多因子引起的血管舒缩反应与血管平滑肌上的KATP有关 ,此信号途径与PKA、PKC等磷酸化激酶有密切联系。不同血管对钾通道开放剂(potassiumchannelopeners,KCO)的反应有差异 ,KCO对血管的选择性作用机制仍不明确。本文就血管平滑肌KATP的分子结构、电生理、药理学特征、信号转导途径和KCO对血管的选择性作用进行综述     

ATP敏感性钾通道的心肌保护机制研究进展

自心肌细胞膜片钳技术应用以来,Nome 1 983年首先在豚鼠心室肌细胞发现ATP敏感性钾通道(KATP channel)[1],随后证实KATP在缺血再灌注中对心肌细胞具有保护作用,为细胞离子通道的研究开创了崭新的局面,成为临床及基础研究的热点.迄今,对心血管系统ATP敏感性钾通道的调节作用缺乏系统研究,本文就KATP的生理作用、在缺血再灌注及在触发性心律失常中对心室肌细胞的保护机制加以综述,为KATP通道开放的临床应用与基础研究提供理论依据.     

ATP敏感性钾通道开放剂在心肌细胞保护中的作用

综述了ATP敏感性钾通道开放剂在心肌细胞保护方面的研究进展。     

抗心肌缺血药物的新靶点:线粒体ATP敏感性钾通道

ATP敏感性钾通道 (KATP)是心脏保护作用的调节位点。随着KATP药理学和分子生物学特征的深入研究 ,发现KATP开放剂介导的心脏保护机制并不依赖于动作电位时程(APD)的缩短和负性肌力作用 ,而与线粒体功能有关。细胞内存在线粒体KATP(mitoKATP)。mitoKATP开放的心脏保护作用机制尚不十分清楚 ,可能与K+ 内流 ,线粒体膜去极化 ,降低Ca2 + 超载 ,基质容积增加有关 ,后者可增加ATP合成、促进线粒体呼吸     

刺五加叶皂苷对心肌ATP敏感性钾通道的作用

目的 :研究刺五加叶皂苷 (ASS)对心肌线粒体ATP敏感性钾通道 (mitoKATP)和细胞膜ATP敏感性钾通道 (sarcolKATP)的作用 ,探讨ASS对缺血心肌保护作用的机制。方法 :用酶解法获取兔心室肌细胞 ,激光扫描共聚焦显微镜观察ASS对mitoKATP 的作用 ,全细胞膜片钳技术观察ASS对sarcolKATP的作用。结果 :对照组观察 10min线粒体荧光强度无明显变化。ASS 30、10 0和 30 0mg·L-1组均可见用药后线粒体荧光强度明显增加 ,分别增加 (14 .8±3.6 ) %、 (30 .4± 4 .3) %和 (38.4± 5 .7) %。3μmol·L-1格列本脲不影响线粒体荧光强度 ,但可以阻断ASS对线粒体荧光强度的作用。而对照组、ASS 10、10 0和 30 0 μmol·L-1组的IK ATP峰值无明显差异。结论 :ASS对mitoKATP有开放作用 ,而对sarcolKATP没有作用。ASS通过开放mitoKATP产生心肌保护作用。     

银杏内酯对脑缺血再灌注大鼠线粒体ATP敏感性钾通道的影响

目的研究银杏内酯抗脑缺血再灌注损伤作用与线粒体ATP敏感性钾通道（mitoK-ATP）开放的关系。方法用Longa法制作大鼠局灶性脑缺血-再灌注损伤模型。造模前静脉给予银杏内酯15mg·kg^-1和（或）选择性mito K—ATP拮抗剂5羟基癸酸（5-HD）10mg·kg^-1预处理,以脑梗死体积、神经缺陷评分、SOD活性和丙二醛含量评价银杏叶提取物抗脑缺血再灌注损伤的作用与mitoKATP开放的关系。结果银杏内酯能够改善大鼠缺血一再灌注引起的脑功能和组织损伤,但此作用可被预先给予的5-HD减弱。结论银杏内酯抗脑缺血一再灌注损伤作用与mitoK-ATP开放有关。     

ATP敏感性钾通道在药理预适应心肌保护中的作用研究进展

心肌保护的有效措施是建立在对心肌缺血(Ischemia)及缺血,再灌注(Ischemia／Reperfusion,I／R)损伤深入认识的基础上,目前认为心肌缺血预处理(IPC)是最强有力的、可再生的内源性心肌保护的有效措施。尽管对。IPC的保护机制仍有争论,但大多数观点认同ATP敏感性钾通道(ATP-sensitive potassium channels)是心肌预处理保护作用的重要环节亦或最终效应器。     

低氧性肺动脉高压中ATP敏感性钾通道的作用

低氧性肺动脉高压（HPH）是肺心病发病的中心环节,有多种因素参与其发生过程,而广泛存在于多种细胞中的ATP敏感性钾通道（KATP）在低氧性肺动脉高压中的作用近年来受到越来越多的关注。KATP是由磺酰脲受体（SUR）和内向整流钾通道（Kir6．x）亚单位组成的异源八聚体,在机体病理情况下发挥调节肺血管张力的重要作用,其活性受多种因素的调控。KATP对于低氧性肺动脉高压的预防和治疗研究有着重要的指导意义。     

心房颤动患者心房组织ATP敏感性钾通道基因转录表达的研究

目的 探讨心房颤动患者心房组织ATP敏感性钾通道(Kir6.2)基因转录的变化。方法 35例风湿性心瓣膜病患者,心外科手术时被取右心耳组织。通过逆转录-聚合酶链反应,以三磷酸甘油醛脱氢酶(GAPDH)为内参照,测量心耳组织Kir6.2通道的mRNA表达量。结果 窦性心律组和阵发性房颤组心房组织Kit6.2的mRNA水平均显著高于慢性房颤组(P<0.05);而阵发性房颤组心房组织Kir6.2的mRNA又显著高于窦性心律组(P<0.05)。结论 Kir6.2通道转录水平的改变可能是相应ATP敏感性钾通道产生的内向整流钾电流(IKATP)重构的分子基础,Kir6.2基因转录改变可能是促进房颤发生和持续的因素之一。     

Neuroprotective role of ATP-sensitive potassium channels in cerebral ischemia

ATP-sensitive potassium (K_ATP) channels are weak, inward rectifiers that couple metabolic status to cell membrane electrical activity, thus modulating many cellular functions. An increase in the ADP/ATP ratio opens K_ATP channels, leading to membrane hyperpolarization. K_ATP channels are ubiquitously expressed in neurons located in different regions of the brain, including the hippocampus and cortex. Brief hypoxia triggers membrane hyperpolarization in these central neurons. In vivo animal studies confirmed that knocking out the Kir6.2 subunit of the K_ATP channels increases ischemic infarction, and overexpression of the Kir6.2 subunit reduces neuronal injury from ischemic insults. These findings provide the basis for a practical strategy whereby activation of endogenous K_ATP channels reduces cellular damage resulting from cerebral ischemic stroke. K_ATP channel modulators may prove to be clinically useful as part of a combination therapy for stroke management in the future.     

ATP-sensitive potassium channels

ATP-sensitive potassium (K(ATP)) channels link membrane excitability to metabolism. They are regulated by intracellular nucleotides and by other factors including membrane phospholipids, protein kinases and phosphatases. K(ATP) channels comprise octamers of four Kir6 pore-forming subunits associated with four sulphonylurea receptor subunits. The exact subunit composition differs between the tissues in which the channels are expressed, which include pancreas, cardiac, smooth and skeletal muscle and brain. K(ATP) channels are targets for antidiabetic sulphonylurea blockers, and for channel opening drugs that are used as antianginals and antihypertensives. This review focuses on non-pancreatic K(ATP) channels. In vascular smooth muscle, K(ATP) channels are extensively regulated by signalling pathways and cause vasodilation, contributing both to resting blood flow and vasodilator-induced increases in flow. Similarly, K(ATP) channel activation relaxes smooth muscle of the bladder, gastrointestinal tract and airways. In cardiac muscle, sarcolemmal K(ATP) channels open to protect cells under stress conditions such as ischaemia or exercise, and appear central to the protection induced by ischaemic preconditioning (IPC). Mitochondrial K(ATP) channels are also strongly implicated in IPC, but clarification of their exact role awaits information on their molecular structure. Skeletal muscle K(ATP) channels play roles in fatigue and recovery, K+ efflux, and glucose uptake, while neuronal channels may provide ischaemic protection and underlie the glucose-responsiveness of hypothalamic neurones. Current therapeutic considerations include the use of K(ATP) openers to protect cardiac muscle, attempts to develop openers selective for airway or bladder, and the question of whether block of extra-pancreatic K(ATP) channels may cause adverse cardiovascular side-effects of sulphonylureas.     

The role of ATP-sensitive potassium channels in the mechanism of ischemic preconditioning.

We clarified the role of K(ATP) channels in the mechanism of ischemic preconditioning by using K(ATP) channel opener, nicorandil, and K(ATP) channel inhibitor, glibenclamide. Forty anesthetized dogs were divided into five groups: (a) control (C), (b) ischemic preconditioning (PC), (c) intravenous infusion of nicorandil before PC (Ni), (d) glibenclamide pretreated with PC (Gl + PC), and (e) glibenclamide pretreated with Ni (Gl + Ni). All groups were followed by 60-min ischemia and 60-min reperfusion and analyzed by the biochemical procedures. At the end of 60-min reperfusion, percentage of segment shortening in C indicated paradoxic bulging. This value was significantly recovered in PC and Ni, but it was still negative in Gl + PC and Gl + Ni. Ca2+ -adenosine triphosphatase (ATPase) activity of sarcoplasmic reticulum (SR) was significantly decreased in C. In PC and Ni, this activity was significantly maintained; however, in Gl + PC and Gl + Ni, it was similar to that in C. State III respiration of mitochondria showed similarity to the changes in SR. These results indicated that the K(ATP) channel opener enhanced the effects of ischemic preconditioning, and its blockade abolished these phenomena. We conclude that the ATP-sensitive potassium channel may play one of key roles in the mechanisms of ischemic preconditioning in the dog model.     

Possible neuroprotective role of arachidonic acidsensitive potassium channels in rat acute cerebral ischemia

AIM: To explore the actual role of arachidonic acid-sensitive potassium channels including TREK- 1, TREK-2 and TRAAK in acute cerebral ischemia. METHODS: In acute rat MCAO model, RT-PCR and Western blot analysis were used to investigate the expression changes of TREK. Immunohistochemistry experiments were also used to study their protein expressions in vivo. RESULTS: TREK-1, TREK-2 and TRAAK mRNA expression     

The role of ATP-sensitive potassium channels in cellular function and protection in the cardiovascular system

ATP-sensitive potassium channels (K_ATP) are widely distributed and present in a number of tissues including muscle, pancreatic beta cells and the brain. Their activity is regulated by adenine nucleotides, characteristically being activated by falling ATP and rising ADP levels. Thus, they link cellular metabolism with membrane excitability. Recent studies using genetically modified mice and genomic studies in patients have implicated K_ATP channels in a number of physiological and pathological processes. In this review, we focus on their role in cellular function and protection particularly in the cardiovascular system.     

ATP敏感性钾通道与心肌缺血预适应

ATP敏感性钾通道 (KATP通道 )作为心肌缺血预适应(早期与延迟效应 )细胞内信号转导途径中的一种“终末效应子” ,在缺血预适应中起重要作用。缺血预适应通过活化心肌细胞膜和 (或 )线粒体膜KATP通道而发挥保护作用。动物实验和临床研究均已证明KATP通道开放剂诱导预适应能有效地防治心肌缺血损伤。     

Inhibition of ATP-sensitive potassium channels by haloperidol

Chronic haloperidol treatment has been associated with an increased incidence of glucose intolerance and type-II diabetes mellitus. We studied the effects of haloperidol on native ATP-sensitive potassium (K(ATP)) channels in mouse pancreatic beta cells and on cloned Kir6.2/SUR1 channels expressed in HEK293 cells. The inhibitory effect of haloperidol on the K(ATP) channel was not mediated via the D2 receptor signaling pathway, as both D2 agonists and antagonists blocked the channel. K(ATP) currents were studied using the patch-clamp technique in whole-cell and outside-out patch configurations. Addition of haloperidol to the extracellular solution inhibited the K(ATP) conductance immediately, in a reversible and voltage-independent manner. Haloperidol did not block the channel when applied intracellularly in whole-cell recordings. Haloperidol blocked cloned Kir6.2/SUR1 and Kir6.2DeltaC36 K(ATP) channels expressed in HEK cells. This suggests that the drug interacts with the Kir6.2 subunit of the channel. The IC(50) for inhibition of the K(ATP) current by haloperidol was 1.6 microM in 2 mM extracellular K(+) concentration ([K(+)](o)) and increased to 23.9 microM in 150 mM [K(+)](o). The Hill coefficient was close to unity, suggesting that the binding of a single molecule of haloperidol is sufficient to close the channel. Haloperidol block of K(ATP) channels may contribute to the side effects of this drug when used therapeutically.     

神经元ATP敏感钾通道的研究进展

ATP敏感性钾离子通道 (KATP,ATPsensitivepotassi umchannel)广泛存在于包括脑在内的多种组织细胞上。该通道是由磺酰脲受体 (SUR ,sulphonylureareceptor)和内向整流钾通道 (Kir,inwardlyrectifyingpotassiumchannel)亚单位组成的异源四聚体 (SUR/Kir6) 4,其活性可被细胞内ATP调控。脑内的KATP通道在生理状态下可介导中枢糖敏感性及代谢应激过程 ,在脑缺血、帕金森病等急慢性神经疾病中同样发挥重要作用     

ATP敏感钾通道亚单位在大鼠组织中的表达

目的　研究ATP敏感钾通道 (KATP)亚单位在大鼠组织中的表达。方法　逆转录多聚酶链式反应 (RT PCR)检测通道mRNA的表达。结果　左心室有Kir 6 1,Kir 6 2和SUR 2A的表达 ,大脑皮层中Kir 6 1,Kir 6 2 ,SUR 1,SUR2B均有表达 ,主动脉平滑肌有Kir 6 1,Kir 6 2 ,SUR 2B的表达 ,膀胱平滑肌中有Kir 6 1,Kir 6 2 ,SUR 2B的表达。结论　各组织的KATP组成有所不同 ,Kir 6 1、Kir 6 2和SUR 2B亚单位在多组织中广泛表达。     

The effects of cromakalim on ATP-sensitive potassium channels in insulin-secreting cells.

1. The single-channel current recording technique has been used to investigate the effects of cromakalim, diazoxide and ATP, separately and combined, on the opening of ATP-sensitive potassium channels in the insulin-secreting cell-line RINm5F. The actions of these drugs have been studied using the permeabilized open-cell variation of the patch-clamp technique. 2. In the absence of internal ATP, cromakalim (80-200 microM) was unable to open ATP-sensitive K+ channels but when ATP was present both cromakalim and diazoxide caused channel openings. 3. Interactions between ATP and cromakalim seemed competitive. Concentrations of cromakalim in the range 80-200 microM readily activated channels inhibited by 0.1 mM ATP, but had no effects when the concentration of ATP was increased to 0.5-2 mM. Only when the concentration of cromakalim was increased to 400-800 microM could opening of 0.5-2 mM ATP-inhibited channels be regularly observed. In the continued presence of cromakalim (400-800 microM), an increase in the internal concentration of ATP from either 0.25 to 0.5 mM or 1 to 2 mM, inhibited cromakalim-activated K+ channels. 4. Activation of ATP-inhibited K+ channels was abolished by replacing ATP with ATP gamma S and cromakalin had no effects on ATP gamma S-inhibited channels. This suggests that cromakalim may open KATP channels in insulin-secreting cells by a mechanism which involves protein phosphorylation.