地尔硫卓对Kvl．4钾通道动力学的影响

目的：研究地尔硫卓对异源表达在卯母细胞上的克隆fKvl．4钾通道电流的激活及失活动力学影响。方法：在非洲爪蟾卵母细胞上异源表达雪貂心脏来源的去N端Kvl．4（fKvl．4△N）通道基因,采用双电极电压钳制技术记录电流、记录药物对fKvl．4AN通道电流的影响。结果：地尔硫卓以频率依赖性、电压依赖性及浓度依赖性的方式抑制fKvl．4△N通道电流,其半抑制浓度（IC50）为（241．04±23．06）μmo]／L（＋50mV）。对照条件下,fKvl．4△N通道电流失活的表现为单指数方程拟合,在应用地尔硫卓后,fKvl．4△N通道电流失活变为双指数方程拟合,即药物诱导的快速失活成分及较慢的C型失活成分。地尔硫卓可加快C型失活,但其不影响fKvl．4△N通道电流的激活过程。结论：地尔硫卓为fKvl．4△N通道的开放状态阻滞剂,可加快Kvl．4△N通道的失活过程。     

普罗帕酮对Kv1.4通道内口突变前后的影响

目的探讨普罗帕酮对编码瞬时外向钾电流(Ito)慢通道Kv1.4通道(fKv1.4ΔN)内口突变(fKv1.4[V561A]ΔN)前后的影响。方法将fKv1.4ΔN和fKv1.4[V561A]ΔN的cRNA注射到非洲爪蟾卵母细胞,孵育24～72 h后使用不同刺激程序用双微电极法记录通道电流的表达。用Clampfit 9.0对数据进行分析。部分电流用相应的方程拟合。结果普罗帕酮对fKv1.4ΔN和fKv1.4[V561A]ΔN的阻滞效应都呈电压和频率依赖性。通道内口的V561A突变使fKv1.4ΔN通道与普罗帕酮的结合能力减小,50%抑制浓度(IC50)在突变前后分别为100μmol/L和380μmol/L(P<0.01)。普罗帕酮能改变fKv1.4ΔN和fKv1.4[V561A]ΔN的失活特性。尽管普罗帕酮对fKv1.4ΔN的失活后恢复没有影响,但是它能延长fKv1.4[V561A]ΔN的50%失活后恢复时间。结论普罗帕酮是fKv1.4ΔN通道的开放通道阻滞剂,fKv1.4ΔN通道内口突变(V561A)能改变普罗帕酮与通道之间的结合能力,从而影响通道的失活和失活后恢复。     

姜黄素对Kv1.4钾通道C型失活的影响

目的研究姜黄素对去N端Kv1.4(Kv1.4ΔN)通道C型失活特性的影响。方法将Kv1.4ΔN的mR-NA注射入非洲爪蟾卵母细胞并于18～20℃下孵育,成功表达后使用双微电极钳制法记录电流,观察姜黄素对Kv1.4ΔN电流失活、复活的影响。结果①姜黄素对Kv1.4ΔN峰电流的抑制作用呈电压依赖性。②姜黄素对Kv1.4ΔN通道失活速度无明显影响。姜黄素灌流前后失活时间常数变化不大(2765±118msvs2513±193ms,n=5,P>0.05)。③通道失活后的恢复时间延长。结论姜黄素抑制钾电流并延长其恢复时间,但对稳态失活并无明显影响。其机制可能与它对通道的开放状态比失活态有更高的亲和力有关。     

姜黄素对Kvl．4钾通道C型失活的影响

目的 研究姜黄素对去N端Kv1.4(Kv1.4△N)通道C型失活特性的影响.方法 将Kv1.4△N的mR-NA注射入非洲爪蟾卵母细胞并于18～20℃下孵育,成功表达后使用双微电极钳制法记录电流,观察姜黄素对Kv1.4△N电流失活、复活的影响.结果 ①姜黄素对Kv1.4△N峰电流的抑制作用呈电压依赖性.②姜黄素对Kv1.4△N通道失活速度无明显影响.姜黄素灌流前后失活时间常数变化不大(2 765±118 ms vs 2 513±193 ms,n=5,P＞0.05).③通道失活后的恢复时间延长.结论 姜黄素抑制钾电流并延长其恢复时间,但对稳态失活并无明显影响.其机制可能与它对通道的开放状态比失活态有更高的亲和力有关.     

参松养心胶囊对Kv1.4钾电流特性的影响

目的: 探讨中药复方制剂参松养心胶囊对KV1.4钾通道C型(KV1.4△N)失活的影响。方法: 将Kv1.4ΔN mRNA注射入非洲爪蟾卵母细胞中,使用双电极钳制法（Two electrodes voltage clamp TEV）观察参松养心胶囊对KV1.4ΔN电生理特性的影响 。结果: 参松养心胶囊对Kv1.4ΔN通道的峰电流有抑制作用,这种阻滞作用具有电压依赖性,随电位的升高而作用加强,符合单指数和线性关系。参松养心胶囊可加速KV1.4ΔN钾通道电流的失活过程,同时可使KV1.4ΔN通道失活后的恢复减慢 。结论: 参松养心胶囊能显著抑制KV1.4钾通道电流,这可能是其抗心律失常作用的机制之一。     

普罗帕酮对Kv1.4ΔN钾通道的作用及细胞外钾离子和pH浓度变化时的影响

目的:探讨抗心律失常药物普罗帕酮对Kv1.4△N钾通道的作用,以及细胞外钾离子和pH浓度变化时对该作用的影响,并探讨该作用可能的机制.方法:将Kv1.4ΔN的mRNA注射入非洲爪蟾卵母细胞并使用双电极钳制法观察普罗帕酮对Kv1.4ΔN电生理特性的影响,以及细胞外钾离子和pH变化时的电生理特性改变.结果:pH7 4状态下,普罗帕酮对Kv1.4ΔN通道的峰电流有抑制作用,这种阻滞作用具有电压依赖性、浓度依赖性以及频率依赖性,并且随电位的升高而作用加强,符合单指数和线性关系.普罗帕酮加速电流的失活过程.在不同的钾离子浓度下,这种阻滞作用具有pH依赖性,细胞外高钾pH7 4时,不同浓度普罗帕酮灌流显示IC50为121 μmol/L;细胞外酸性环境下(pH6 0)IC50提高到463 μmol/L,碱性化的环境(pH8 0)降至58 μmol/L.结论:普罗帕酮是Kv1.4ΔN的阻滞剂,可能与作用于细胞内的某些位点有关.     

酸中毒时心脏克隆钾离子通道Kv1.4的动力学特性

目的:探讨心脏克隆钾离子通道Kv1.4的C型失活(Kv1.4△N)在非洲蟾蜍卵母细胞上表达后的动力学特性以及酸中毒时的改变. 方法:将Kv1.4△NcRNA(最大体积为50 nl)注入非洲爪蟾的卵母细胞内,于18℃孵育16 h以上.电极采用两步法拉制,微电极由1.5 mm口径的电极拉制.电极内充3M KCl,电阻0.5～1.0MΩ.采用双微电极电压钳制法(two electrode voltage clamp,TEV)在室温下(20～24℃)记录电流. 结果:与正常pH时相比,酸性环境下,Kv1.4△N的峰电流减小,在pH 7.4时通道在去极化至-40mv激活,而pH 6.8时为-30 mv激活;通道在pH 7.4时最大失活为0.384±0.072,而在pH 6.8时为0.197±0.013;在pH 6.8时通道复活减慢(P＜0.05). 结论:酸中毒导致通道电流减小,并且使通道失活加快和恢复减慢.     

替米沙坦对表达在卵母细胞上Kv1.5通道的抑制效应

目的:研究替米沙坦对表达在卵母细胞上的克隆人类Kv1.5通道的作用,探讨其在心脏复极中的潜在效应。方法:在非洲爪蟾卵母细胞上异源表达克隆人类Kv1.5通道基因,使用双电极电压钳技术记录全细胞电流,检测药物对Ikur电流的影响。结果:替米沙坦以电压依赖性和浓度依赖性方式抑制Kv1.5通道电流,且对峰电流及1.5s末端电流的抑制效应不同,在1μmol/L浓度下,抑制效应分别达到(7.75±2.39)和(52.64±3.77),其半抑制浓度(IC50)分别为(2.25±0.97)μmol/L和(0.82±0.39)μmol/L。替米沙坦对通道的稳态失活没有显著改变,在对照条件下,V1/2的值为(14.47±3.71)mV,斜坡因子k为(23.24±3.86)mV;在1μmol/L替米沙坦作用下,V1/2和k的值分别为(14.38±4.62)mV和(26.26±5.04)mV(n=6,P>0.05)。同时,替米沙坦显著加速了Kv1.5通道的失活。在对照条件下,Kv1.5通道的失活慢时间常数是(693.74±23.16)ms,在应用1μmol/L替米沙坦后,其失活的慢时间常数下降为(523.85±10.28)ms(n=5,P<0.05)。结论:替米沙坦在临床有效浓度范围内能显著抑制表达在卵母细胞上的Ikur电流,提示它兼有选择性阻滞Kv1.5通道的作用。     

Kvβ1.3亚基显著影响DPO-1对表达在卵母细胞上的Kvl.5通道的阻断作用

目的:研究Kvβ1.3亚基和Kv1.5共表达时,对表达在非洲爪蟾卵母细胞的Kv1.5通道DPO-1的阻断作用的影响。方法:在非洲爪蟾卵母细胞上异源表达克隆Kv1.5及Kvβ1.3通道基因,用双电极电压钳技术记录全细胞电流,检测药物对Kv1.5通道及Kv1.5+Kvβ1.3共表达通道电流的影响。结果:DPO-1以电压、频率及浓度依赖方式抑制Kv1.5+Kvβ1.3共表达通道的电流。Kvβ1.3亚基存在时,DPO-1的阻断效应明显减弱,DPO-1阻断的IC50由(0.77士0.12)μmol/L显著增加至(47.21士5.18)μmol/L,增加了约60倍(P<0.01)。结论:Kvβ1.3亚基显著抑制DPO-1对表达在卵母细胞上的Kv1.5通道的阻断作用,但不改变其电压、频率及浓度依赖性,可能机制是Kvβ1.3亚基与DPO-1相互竞争Kv1.5孔区内部的某些结合位点。     

Kvβ1.3亚基显著影响DPO-1对表达在卵母细胞上的Kv1.5通道的阻断作用

目的:研究Kvβ1.3亚基和Kv1.5共表达时,对表达在非洲爪蟾卵母细胞的Kv1.5通道DPO-1的阻断作用的影响。方法:在非洲爪蟾卵母细胞上异源表达克隆Kv1.5及Kvβ1.3通道基因,用双电极电压钳技术记录全细胞电流,检测药物对Kv1.5通道及Kv1.5+Kvβ1.3共表达通道电流的影响。结果:DPO-1以电压、频率及浓度依赖方式抑制Kv1.5+Kvβ1.3共表达通道的电流。Kvβ1.3亚基存在时,DPO-1的阻断效应明显减弱,DPO-1阻断的IC50由(0.77士0.12)μmol/L显著增加至(47.21士5.18)μmol/L,增加了约60倍(P0.01)。结论:Kvβ1.3亚基显著抑制DPO-1对表达在卵母细胞上的Kv1.5通道的阻断作用,但不改变其电压、频率及浓度依赖性,可能机制是Kvβ1.3亚基与DPO-1相互竞争Kv1.5孔区内部的某些结合位点。     

Diltiazem inhibits hKv1.5 and Kv4.3 currents at therapeutic concentrations

OBJECTIVE: In the present study we examined the effects of diltiazem, an L-type Ca(2+) channel blocker widely used for the control of the ventricular rate in patients with supraventricular arrhythmias, on hKv1.5 and Kv4.3 channels that generate the cardiac ultrarapid delayed rectifier (I(Kur)) and the 4-aminopyridine sensitive transient outward (I(to)) K(+) currents, respectively. METHODS: hKv1.5 and Kv4.3 channels were stably and transiently expressed in mouse fibroblast and Chinese hamster ovary cells, respectively. Currents were recorded using the whole-cell patch clamp. RESULTS: Diltiazem (0.01 nM-500 muM) blocked hKv1.5 channels, in a frequency-dependent manner exhibiting a biphasic dose-response curve (IC(50)=4.8+/-1.5 nM and 42.3+/-3.6 muM). Diltiazem delayed the initial phase of the tail current decline and shifted the midpoint of the activation (Vh=-16.5+/-2.1 mV vs -20.4+/-2.6 mV, P<0.001) and inactivation (Vh=-22.4+/-0.7 mV vs. -28.2+/-1.9 mV, P<0.001) curves to more negative potentials. The analysis of the development of the diltiazem-induced block yielded apparent association (k) and dissociation (P) rate constants of (1.6+/-0.2) x 10(6) M(-1)s(-1) and 46.8+/-4.8 s(-1), respectively. Diltiazem (0.1 nM-100 muM) also blocked Kv4.3 channels in a frequency-dependent manner exhibiting a biphasic dose-response curve (IC(50)=62.6+/-11.1 nM and 109.9+/-12.8 muM). Diltiazem decreased the peak current and, at concentrations > or =0.1 microM, accelerated the inactivation time course. The apparent association and dissociation rate constants resulted (1.7+/-0.2) x 10(6) M(-1)s(-1) and 258.6+/-38.1 s(-1), respectively. Diltiazem, 10 nM, shifted to more negative potentials the voltage-dependence of Kv4.3 channel inactivation (Vh=-33.1+/-2.3 mV vs -38.2+/-3.5 mV, n=6, Plt;0.05) the blockade increasing at potentials at which the amount of inactivated channels increased. CONCLUSION: The results demonstrated for the first time that diltiazem, at therapeutic concentrations, decreased hKv1.5 and Kv4.3 currents by binding to the open and the inactivated state of the channels.     

替米沙坦对电压依赖性的Kv1.3和Kv1.5通道电流阻断作用的实验研究

目的 通过观察替米沙坦对电压依赖性的Kv1.3和Kv1.5的阻断作用,探讨替米沙坦对此类通道的阻断可能具有的临床作用.方法 使用双电极电压钳技术记录表达于非洲爪蟾卵母细胞的Kv1.3和Kv1.5钾通道电流,不同浓度灌流观察其对电流影响.结果 (1)替米沙坦浓度依赖性的阻断Kv1.3通道,其阻断的IC50是2.05 μmol/L.替米沙坦对Kv1.3电流的阻断具有电压依赖性.(2)替米沙坦浓度依赖件的阻断Kv1.5通道,其阻断的IC50是2.37 μmol/L.替米沙坦对Kv1.5电流的阻断具有更显著的电压依赖性.结论 替米沙坦阻断开放状态的Kv1.3可能是其发挥免疫调节和抗动脉粥样硬化作用的机制之一.替米沙坦对开放状态的Kv1.5钾通道的阻断可能是其减少心房颤动发生率的作用机制之一.     

厄贝沙坦对电压依赖性的Kv1.3和Kv1.5通道电流的阻断作用

目的通过观察厄贝沙坦对电压依赖性的Kv1.3和Kv1.5的阻断作用,探讨厄贝沙坦对此类通道的阻断可能具有的临床作用。方法使用双电极电压钳技术记录表达于非洲爪蟾卵母细胞的Kv1.3和Kv1.5钾通道电流,不同浓度厄贝沙坦灌流对其电流的影响。结果①厄贝沙坦浓度依赖性的阻断Kv1.3通道,阻断的IC50是2.46μmol/L,且阻断具有电压依赖性。②厄贝沙坦浓度依赖性的阻断Kv1.5通道,阻断的IC50是0.47μmol/L,且阻断具有显著的电压依赖性。结论厄贝沙坦阻断开放状态的Kv1.3可能是其发挥免疫调节和抗动脉粥样硬化作用的机制之一;而对开放状态的Kv1.5的阻断可能是其具备减少心房颤动发生率的作用机制之一。     

盐酸关附甲素对转染HERG基因表达的快速激活延迟整流钾通道电流的影响

目的 用膜片钳全细胞记录法观察盐酸关附甲素(AHH)对转染HERG基因表达的快速激活延迟整流钾电流(IKr)的影响.方法 使用脂质体介导的瞬时转染法把野生型HERG基因转染人人胚肾细胞(HEK293),采用标准的全细胞膜片钳技术记录IKr通道电流,观察不同浓度的AHH对IKr的影响.结果 AHH对IKr通道的峰电流IHERC具有浓度和电压依赖性抑制作用,半数最大抑制浓度(IC50)为465.95 μmol/L;400 μmol/L的AHH使IHERG的最大峰值电位前移,但不改变激活电位.25、100、400、1000、2500 μmol/L的AHH对尾电流(Itail)抑制率分别为1.53%、13.60%、-5.92%、30.14%、38.51%.100和400 μmol/L的AHH使激活曲线左移并能加快通道的失活.结论 25～400 μmol/L的AHH对IKr的抑制作用不明显;AHH主要是作用于IKr通道的失活态.     

Diltiazem facilitates inactivation of single L-type calcium channels in guinea pig ventricular myocytes

Diltiazem is a benzothiazepine Ca2+ channel blocker used clinically for its antihypertensive and antiarrhythmic effects. We studied the mechanism of diltiazem blockade by recording L-type Ca2+ channel currents from cell-attached patches in isolated guinea pig ventricular myocytes using Ba2+ as the charge carrier. With diltiazem (200 microM) in the superfusate, multichannel currents showed a use-dependent decline in amplitude reflecting reductions in the numbers of superpositions of channel openings. Analysis of single-channel currents revealed that both open and closed times were little affected by diltiazem (50 and 100 microM). However, the rate of decay of the averaged current during 150-ms depolarization steps was significantly accelerated and the open state probability in current containing-sweeps was significantly decreased by diltiazem, suggesting that the drug accelerates transition from the activated state to the inactivated state. The effect of diltiazem on the slow gating process was studied by repetitively applying 500-1000 step pulses at selected holding potentials. Decreased channel availability by diltiazem was reflected by the increasing number of blank sweeps per run at depolarized holding potentials. These results suggest that diltiazem reduces Ca2+ influx by accelerating inactivation during action potentials, and that the use-dependent blockade is due to increases in the number of channels in a sustained closed state.     

Kv1.4通道电流与大鼠心室肌细胞瞬间外向钾电流特性的比较

克隆的大鼠外向钾通道Ｋｖ１．４亚型表达于２９３细胞（ＲＣＫ４）。用膜片钳全细胞钳制法系统比较该克隆的大鼠瞬间外向钾电流（Ｉｔｏ）和天然大鼠心室肌细胞Ｉｔｏ的特点和动力学特性。两种通道电流形态相似,呈“Ａ”型电流,在＋４０ｍＶ时电流失活时间常数τ依次为３６．６±２ｍｓ和４１．０±２ｍｓ（Ｐ＞０．０５）。Ｋｖ１．４通道电流激活曲线用二相Ｂｏｌｔｚｍａｎｎ方程拟合,一相半数最大激活电位（Ｖ１／２,１）为－２１．０±３．９ｍＶ、二相半数最大激活电位（Ｖ１／２,２）为２７．０±３．９ｍＶ;天然大鼠心室肌细胞Ｉｔｏ激活曲线用单相Ｂｏｌｔｚｍａｎｎ方程拟合,半数最大激活电位为１０．８±１．１ｍＶ（Ｐ＜０．０５,ｖｓＫｖ１．４通道电流的Ｖ１／２,１）。ＲＣＫ４细胞通道电流半数最大灭活电位（Ｖ１／２）为－４９．８±１．８ｍＶ,斜率因子（ｋ）为３．８±０．２７;天然大鼠心室肌细胞Ｉｔｏ的Ｖ１／２为－３１．６±１．７ｍＶ,ｋ为５．４±０．２１。灭活后再激活的恢复时间比较,Ｋｖ１．４通道电流明显长于天然大鼠心室肌细胞Ｉｔｏ,分别为１．８９±０．２ｓ和３９．２±１．６ｍｓ（Ｐ＜０．０５）。研究表明克隆的大鼠Ｋｖ１．４通道电流与天然大?     

Elimination of fast inactivation in Kv4 A-type potassium channels by an auxiliary subunit domain

The Kv4 A-type potassium currents contribute to controlling the frequency of slow repetitive firing and back-propagation of action potentials in neurons and shape the action potential in heart. Kv4 currents exhibit rapid activation and inactivation and are specifically modulated by K-channel interacting proteins (KChIPs). Here we report the discovery and functional characterization of a modular K-channel inactivation suppressor (KIS) domain located in the first 34 aa of an additional KChIP (KChIP4a). Coexpression of KChIP4a with Kv4 alpha-subunits abolishes fast inactivation of the Kv4 currents in various cell types, including cerebellar granule neurons. Kinetic analysis shows that the KIS domain delays Kv4.3 opening, but once the channel is open, it disrupts rapid inactivation and slows Kv4.3 closing. Accordingly, KChIP4a increases the open probability of single Kv4.3 channels. The net effects of KChIP4a and KChIP1-3 on Kv4 gating are quite different. When both KChIP4a and KChIP1 are present, the Kv4.3 current shows mixed inactivation profiles dependent on KChIP4a/KChIP1 ratios. The KIS domain effectively converts the A-type Kv4 current to a slowly inactivating delayed rectifier-type potassium current. This conversion is opposite to that mediated by the Kv1-specific "ball" domain of the Kv beta 1 subunit. Together, these results demonstrate that specific auxiliary subunits with distinct functions actively modulate gating of potassium channels that govern membrane excitability.