苄基四氢巴马汀对豚鼠心室肌细胞钾电流及钙、钠电流的作用

目的：研究苄基四氢巴马汀（BTHP）对心肌细胞的作用特点,以探讨其抗心律失常机制。方法：用全细胞膜片钳技术考察BTHP对心室肌细胞钾电流及钙、钠电流的作用。结果：BTHP 30 μmol.L^-1明显阻滞延迟整流钾电流（I_K包括：I_Kr及I_Ks）。可使I_Kr及I_Kr,tail的幅值下降,且对I_Kr阻滞作用呈频率依赖性;对I_Ks及I_Ks,tail幅值也有明显的抑制作用。BTHP 200　μmol.L^-1可明显阻滞I_Ca,L,使其电流幅值降低,但对I_K1,I_Ca,T,I_Na电流均无影响。结论：BTHP可明显阻滞心室肌细胞I_Kr,I_Ks,I_Ca,L电流,且对I_Kr阻滞作用呈频率依赖性。     

苄普地尔对豚鼠甲亢性肥厚心肌中延迟整流钾电流的抑制作用

目的　研究苄普地尔(bepridil)对肥厚心肌细胞延迟整流钾电流(I_K)中快激活成份(I_Kr)和慢激活成份(I_Ks)及内向整流钾电流(I_K1)的作用。方法　全细胞膜片钳技术。结果　在肥厚心肌细胞中,Bepridil 30 μmol·L- 1 对I_Kr及I_Ks有阻断作用,抑制率分别为20.9% (0 mV)和27.2 % (+50 mV)。“Envelopeoftail”显示bepridil对I_Ks的阻断作用大于I_Kr。Bepridil(1 - 100 μmol·L^-1 )浓度依赖性的阻断I_Ks及I_Kr,其IC₅₀ 分别为23.8μmol·L^-1 和46.7μmol·L^-1 。Bepridil 30 μmol·L^-1 也能阻断I_K1 ,抑制率为15.1% (- 100 mV) ,但不影响其反转电位。结论　Bepridil对甲亢性豚鼠肥厚心肌中I_Ks,I_Kr及I_K1有阻断作用     

III类抗心律失常药RP58866对豚鼠及犬内向整流及瞬时外向钾电流的作用

目的:研究III类抗心律失常药RP58866 对I_K1 ,瞬时外向钾电流(Ito) 的作用。方法:用豚鼠和犬离体心肌细胞及全细胞电压钳技术。结果:在- 100 m V 时,RP58866 以浓度依赖方式明显减少了豚鼠心室肌细胞I_K1,其IC₅₀为(3-4±0-8) μmol·L^-1。在犬心室肌细胞,RP58866 可明显抑制Ito( 在100 μmol·L^-1 时减少87% ±2-1% ),其IC₅₀为(2-3±0-5) μmol·L^-1 。结论:RP58866 对心肌细胞的IK1 和Ito 均有抑制作用,而不是一种特殊的IK1抑制剂。     

哇巴因和乌头碱诱发豚鼠和大鼠心律失常的离子作用靶点哇巴因和乌头碱诱发豚鼠和大鼠心律失常的离子作用靶点

目的观察哇巴因和乌头碱对豚鼠和大鼠心肌单细胞离子通道的作用,确定两药诱发心律失常时离子靶点和最佳靶点,建立细胞水平的心律失常模型。方法用全细胞膜片钳技术记录哇巴因和乌头碱对酶解法分离的豚鼠和大鼠心肌细胞离子通道的作用。结果5 μmol·L^-1哇巴因使豚鼠心肌细胞APD延长、I_Ca-L增加、I_k减少、I_k1减少;1 μmol·L^-1乌头碱使大鼠心肌细胞APD延长、I_Ca-L增加、I_to减少、I_k1增加。结论哇巴因和乌头碱诱发心律失常的离子靶点有APD,I_Ca-L,I_k,I_to和I_k1,而最佳靶点应为APD,I_Ca-L,I_k 和I_to。在单细胞水平分别应用哇巴因和乌头碱诱发豚鼠和大鼠心律失常,具有稳定性高、条件可控、重复性好等优点,可用于药物筛选和机制研究。     

抗心律失常药物作用的靶点——HERG K+通道

快速延迟整流钾电流(rapidly activating component of delayed rectifier potassium current，I_Kr)在心肌动作电位复极化过程中发挥重要作用。HERG基因编码心脏快速延迟整流钾通道的α亚基，HERG基因突变导致遗传性长QT间期综合征(long QT syndrome，LQTS)，另外I_Kr/HERG通道是绝大多数能引起心脏QT间期延长药物的作用靶标，其他一些化学结构不同的药物也可阻断该通道，引起QT间期延长，甚至发展成获得性心律失常。本文从门控机制及功能、HERG通道相关的心律失常、药物与通道相互作用机制、优化通道靶点的策略等四个方面综述I_Kr/HERG通道在抗心律失常方面的最新研究进展。     

青蒿素抗心律失常的作用机理

采用全细胞电压钳技术, 以确定青蒿素对分离的豚鼠心室肌细胞和狗的浦肯野纤维钾离子电流的影响. 在豚鼠心室肌细胞,青蒿素呈浓度依赖关系显著降低内向整流钾电流〔I_K1,膜电位为-100 mV时, IC₅₀为(7.2±0.8) μmol·L^-1〕,且这种抑制作用不呈现频率依赖性. 50 μmol·L^-1的青蒿素降低延迟整流钾电流(I_K): 时间依赖性外向钾电流(I_Kstep)在膜电位为+40 mV时减少(38±10)%. 尾电流步阶分析提示,I_K的快组分(I_Kr)和慢组分(I_Ks)均被抑制. 在犬浦肯野纤维,青蒿素明显抑制瞬时外向钾电流(I_to),IC₅₀为(4.2±0.3) μmol·L^-1. 实验结果表明,青蒿素以相似效率抑制I_K1, I_to和I_K,其抗心律失常作用可能与抑制I_K1,I_to,I_Kr和I_Ks有关.     

阿米洛利对豚鼠心肌细胞钾电流及钙电流的作用

目的研究阿米洛利（amiloride）对豚鼠心肌细胞钾电流及钙电流的作用。方法采用全细胞膜片钳技术记录豚鼠心室肌细胞钾通道及钙通道电流。结果阿米洛利在10~100 μmol·L^-1抑制L型及T型钙电流,不改变钙电流I-V曲线的形状，仅抑制这两型电流的幅度。当累积浓度达100 μmol·L^-1时，阿米洛利轻微抑制快激活延迟整流钾电流(I_Kr)，对慢激活延迟整流钾电流(I_Ks)无影响。阿米洛利在1~100 μmol·L^-1浓度依赖性地抑制内向整流钾电流(I_K1)。结论阿米洛利抑制电压依赖性的钾、钙电流，为其抗心律失常作用提供了离子基础。     

AMP579与腺苷对大鼠和豚鼠心室肌钾离子或钠离子通道作用的比较

目的研究AMP579和腺苷对钾离子与钠离子通道的影响及其作用机制，比较它们对负性变力及抗心律失常作用的离子机制。方法采用膜片钳全细胞记录模式记录大鼠和豚鼠心室肌细胞离子通道电流。结果腺苷对大鼠心室肌瞬时外向钾电流(I_{to)的激动作用强于AMP579，腺苷和AMP579的EC50值分别为2.33与8.32 μmol·L^-1 (P<0.05)；两者激动Ito的作用均可被腺苷A1受体阻滞剂PD116948阻断，表明其作用机制均是通过腺苷A1受体介导的。腺苷对豚鼠心室肌延迟整流钾电流(IK)的抑制作用强于AMP579，腺苷和AMP579的IC50值分别为1.21与2.31 μmol·L^-1 (P<0.05)；AMP579对内向整流钾电流(IK1)的抑制作用强于腺苷，AMP579和腺苷的IC50值分别为4.15与20.7 μmol·L^-1 (P<0.01)。AMP579和腺苷对大鼠心室肌钠电流(INa)的抑制作用相似，其IC50值分别为9.46与6.23 μmol·L^-1。结论腺苷对大鼠心室肌Ito的激动作用强于AMP579，两者对Ito的作用机制均是通过腺苷A1受体介导的。AMP579对IK1的抑制作用强于腺苷，而腺苷对IK的抑制作用强于AMP579，两者对INa的抑制作用相似，这些离子机制与两者发挥负性变力与抗心律失常作用有关系。}     

牛磺酸镁配合物对获得性长QT综合征模型的抗心律失常作用研究

目的 研究牛磺酸镁配合物（TMCC）对获得性长QT综合征（LQTS）模型的抗心律失常作用及作用机制。方法 采用Langendorff逆行主动脉灌流酶解法,急性分离获得豚鼠单个心室肌细胞;建立表达KCNQ1/KCNE1基因的HEK293细胞模型。色原烷醇293B （5 μmol/L）用来建立LQTS模型,采用全细胞膜片钳技术记录TMCC （0.01、0.10、1.00 mmol/L）对正常和LQTS模型豚鼠心室肌细胞动作电位和缓慢激活延迟整流外向钾通道（I_Ks）电流的影响。结果 色原烷醇293B可以显著延长50%和90%复极化动作电位持续时间（APD₅₀和APD₉₀）,0.01、0.10、1.00 mmol/L TMCC可以显著减弱色原烷醇293B延长APD₅₀和APD₉₀的作用（P<0.05、0.01）。TMCC （0.01、0.10、1.00 mmol/L）对抗色原烷醇293B对I_Ks电流的抑制作用,减弱色原烷醇293B对I-V曲线的下移,0.1、1.0 mmol/L浓度组显著减弱色原烷醇293B对I_Ks电流的抑制作用（P<0.01）,呈现对抗LQTS的作用。结论 TMCC通过缩短动作电位复极时程,增大被抑制的I_Ks电流,发挥一定的抗LQTS的作用。     

抗疟药青蒿素抗心律失常的作用机制

目的：探讨青蒿素抗心律失常的离子电流基础。方法：用全细胞膜片钳技术和双电极电压钳技术。结果：当细胞超极化到-100 mV时,青蒿素以浓度依赖方式明显抑制家兔心室肌细胞I_k1,50μmol.L^-1青蒿素可使家兔心室肌细胞I_k1从对照组的-2.36±0.39　nA减少到-1.43±0.31nA。给予非洲蛙卵母细胞注射K_{ir 2.1}　cRNA后,用不同浓度青蒿素灌注,可减低K_{ir 2.1}钾通道电流,此作用呈电压和浓度依赖性。青蒿素对K_{ir 2.1}钾通道的阻断作用呈可逆性。结论：青蒿素能有效抑制离体心肌细胞I_k1,其抗心律失常作用机理与其抑制心肌细胞I_k1及阻断K_{ir 2.1}通道电流有关。     

RP58866对哺乳动物心室肌细胞跨膜钾电流的作用

AIM: To determine effects of RP58866 on inward rectifier K+ current (IKl), transient outward K+ current (Ito) and delayed outward rectifier K+ current (IK) in isolated cardiac myocytes. METHODS: In isolated ventricular myocytes of guinea pig and dog, the effect of RP58866 on IKl, Ito, and IK were observed by the whole cell voltage-clamp technique. RESULTS: RP58866 decreased IKl in a concentration-dependent manner, with an IC50 of (3.4 +/- 0.8) micromol.L-1 (n = 6) at -100 mV in guinea pig ventricular cells. In dog ventricular myocytes, RP58866 inhibited Ito with IC50 of (2.3 +/- 0.5) micromol.L-1 at +40 mV. In guinea pig ventricular cells, RP58866 at 100 micromol.L-1 decreased IK: IKstep by (58 +/- 13)% at +40 mV, and IKtail by (86 +/- 17)%, respectively. RP58866 inhibited IKstep with an IC50 of (7.5 +/- 0.8) micromol.L-1, and IKtail with an IC50 of (3.5 +/- 0.9) micromol.L-1. The envelope of tail analysis suggested that both IKr and IKs were inhibited. CONCLUSION: RP58866 inhibits IKl, Ito, and IK in cardiac myocytes with a similar potency, and is not a specific IKl inhibitor.     

HMR 1556, a potent and selective blocker of slowly activating delayed rectifier potassium current

The slowly activating delayed rectifier potassium current (IKs) contributes prominently to ventricular repolarization of the cardiac action potential. Development of a selective IKs blocker is important for the elucidation of the physiologic and pathophysiologic relevance of IKs and the development of antiarrhythmic strategies. HMR 1556 [(3R,4S)-(+)-N-[3-hydroxy-2,2-dimethyl-6-(4,4,4-trifluorobutoxy) chroman-4-yl]-N-methylmethanesulfonamide] is a new chromanol derivative developed as a selective IKs blocker. Chromanol 293B, the most specific IKs blocker currently available, also inhibits the transient outward current (Ito). HMR 1556 was examined for its effects on IKs compared with rapidly activating delayed rectifier (IKr), inward rectifier (IK1), Ito, and L-type calcium (ICa.L) currents in canine left ventricular myocytes. HMR 1556 (0.5-500 nM ) inhibited IKs in a concentration-dependent manner (IC50 of 10.5 nM, compared with chromanol 293B's IC50 of 1.8microM). Inhibition of Ito was observed only at relatively high concentrations (IC50 of 33.9 microM comparable to chromanol 293B's IC of 38 microM). High concentrations of HMR 1556 also inhibited ICa.L (IC of 27.5 microM) and IKr (IC50 of 12.6 microM) while IK1 was unaffected. Our results indicate that HMR 1556 is superior to chromanol 293B in its potency and specificity for inhibition of IKs, making it a valuable experimental tool and a potential therapeutic agent.     

苦参碱对豚鼠心肌细胞钾电流的抑制作用(英文)

目的研究苦参碱对豚鼠心肌细胞动作电位时程和钾电流的影响,探讨其抗心律失常作用的可能机制。方法应用全细胞膜片钳技术记录心室肌细胞的动作电位时程和钾电流。结果在频率0.1Hz时,苦参碱100μmol.L-1以非频率依赖方式延长动作电位复极90%的时程达40%,在-120mV抑制内向整流钾电流(IK1)接近47%,减少快激活延迟整流钾电流的尾电流达50%,对慢激活延迟整流钾电流的尾电流无影响。结论苦参碱抗心律失常的机制可能与其抑制多种钾电流和延长动作电位时程有关。     

青蔼素阻断豚鼠心室肌细胞活化和缓慢活化的钾电流

AIM: To study the effect of artemisinin (Art) on outward rectifier potassium current in ventricular myocytes. METHODS: In isolated guinea pig ventricular myocytes, the effects of Art on the two components of delayed outward rectifier K+ current (IK), the rapidly activating inward K+ current (IKr), and the slowly rectifying outward K+ current (IKs) were observed by the whole cell patch-clamp technique. RESULTS: Art decreased IK in a concentration-dependent manner. The IKstep and IKtail were reduced from 387 +/- 46 pA to 240 +/- 48 pA and from 299 +/- 30 pA to 130 +/- 38 pA, respectively at holding potential of +40 mV by Art 50 mumol.L-1. The envelope of tail analysis suggested that both IKr and IKs were inhibited. CONCLUSION: Art blocked the two components of delayed outward rectifier K+ current (IKr and IKs) in guinea pig ventricular cells.     

Increase in action potential duration and inhibition of the delayed rectifier outward current IK by berberine in cat ventricular myocytes.

1. In the present work, the effects of the antiarrhythmic drug, berberine, on action potential and ionic currents of cat ventricular myocytes were studied. 2. Berberine prolonged action potential duration in cat ventricular myocytes without altering other variables of the action potential. 3. The drug at concentrations of 0.3-30 microM blocked only the delayed rectifier (IK) current with an IC50 = 4.1 microM. Berberine produced a tonic block and a phasic block that was increased with the duration of the depolarizing pulse. The blocking effect on IK was use-dependent, but not frequency-dependent. 4. In cardiac preparations two delayed rectifier currents have been found: a rapid (IKr) current and a slow (IKs) current. In the present work it has been found that berberine at the concentrations used, selectively blocked IKr. 5. At concentrations higher than 10 microM it also decreased the transient outward (Ito1) current. The drug did not have effects on the inward rectifier (IK1) or the high threshold calcium current (Ica-L). 6. These results show that berberine is a specific potassium channel blocker. The increase in action potential duration induced by berberine can be explained mainly by its blocking effects on IK.     

Two components of delayed rectifier K^＋ current in heart： molecular basis, functional diversity, and contribution to repolarization

Delayed rectifier K^ current (IK) is the major outward current responsible for ventricular repolarization. Two components of IK (IKr and/Ks) have been identified in many mammalian species including humans. IKr plays a pivotal role in normal ventricular repolarization. A prolongation of action potential duration (APD) under a variety of conditions would favor the activation of IKs so that to prevent excessive repolarization delay causing early afterdepolarization. The pore-forming α subunits of IKr and IKs are composed of HERG (KCNH2) and KvLQT1(KCNQ1), respectively. KvLQT1 is associated with a function-altering β subunit, minK to form IKs. HERG may be associated with minK (KCNE1) and/or minK-related protein (MiRP1) to form IKr, but the issue remains to be established. IKs is enhanced, whereas IKr is usually attenuated by β-adrenergic stimulation via cyclic adenosine 3‘,5‘-monophosphate (cAMP)/protein kinase A-dependent pathways. There exist regional differences in the density of IKr and IKs transmurally (endo-epicardial) and along the apico-basal axis, contributing to the spatial heterogeneity of ventricular repolarization. A decrease of IKr or IKs by mutations in either HERG, KvLQT1, or KCNE family results in inherited long QT syndrome (LQTS) with high risk for Torsades de pointes (TdP)-type polymorphic ventricular tachycardia and ventricular fibrillation. As to the pharmacological treatment and prevention of ventricular tachyarrhythmias, selectively block of IKs is expected to be more beneficial than selectively block of IKr in terms of homogeneous prolongation of refractoriness at high heart rates especially in diseased hearts including myocardial ischemia.     

Effect of the antifibrillatory compound tedisamil (KC-8857) on transmembrane currents in mammalian ventricular myocytes

The cellular mechanism of action of tedisamil (KC-8857) (TED), a novel antiarrhythmic/antifibrillatory compound, was studied on transmembrane currents in guinea pig, rabbit and dog ventricular myocytes by applying the patch-clamp and the conventional microelectrode technique. In guinea pig myocytes the rapid component of the delayed rectifier potassium current (IKr) was largely diminished by 1 microM TED (from 0.88+/-0.17 to 0.23+/-0.07 pA/pF, n=5, p<0.05), while its slow component (IKs) was reduced only by 5 microM TED (from 8.1+/-0.3 to 4.23+/-0.07 pA/pF, n=5, p<0.05). TED did not significantly change the IKr and IKs kinetics. In rabbit myocytes 1 microM TED decreased the amplitude of the transient outward current (I(to)) from 20.3+/-4.9 to 13.9+/-2.8 pA/pF (n=5, p<0.05), accelerated its fast inactivation time constant from 8.3+/-0.6 to 3.5+/-0.5 ms (n=5, p<0.05) and reduced the ATP-activated potassium current (IKATP) from 38.2+/-11.8 to 18.4+/-4.7 pA/pF (activator: 50 microM cromakalim; n=5, p<0.05). In dog myocytes 2 microM TED blocked the fast sodium current (INa) with rapid onset and moderately slow offset kinetics, while the inward rectifier potassium (IK1), the inward calcium (ICa) and even the I(to) currents were not affected by TED in concentration as high as 10 microM. The differences in I(to) responsiveness between dog and rabbit are probably due to the different alpha-subunits of I(to) in these species. It is concluded that inhibition of several transmembrane currents, including IKr, IKs, I(to), IKATP and even INa, can contribute to the high antiarrhythmic/antifibrillatory potency of TED, underlying predominant Class III combined with I A/B type antiarrhythmic characteristics.     

苦参碱与E-4031,多非利特和RP58866对家兔心肌I_(k1)的作用比较(英文)

目的　比较苦参碱与E 4 0 31,多非利特和RP5 886 6对家兔单个心室肌细胞的内向整流钾电流(Ik1)的效价和效能的不同 ,揭示苦参碱抗心律失常作用弱于西药的原因。方法　应用全细胞膜片钳技术记录苦参碱与E 4 0 31,多非利特和RP5 886 6对家兔Ik1的影响。结果　苦参碱 1和 10 μmol·L- 1对家兔Ik1无明显影响。在实验电压为 - 12 0mV和保持电压为 - 70mV ,苦参碱 5 0和 10 0 μmol·L- 1对Ik1分别抑制达 6 % (n =8,P <0 .0 5 )和 8% (n =8,P <0 .0 5 ) ;在实验电压为 - 5 0mV ,抑制Ik1达 4 % (n =8,P <0 .0 5 )和 8% (n =8,P <0 .0 5 )。在实验电压为 - 12 0mV ,E 4 0 311和 10 μmol·L- 1使Ik1分别降低10 % (n =6 ,P <0 .0 5 )和 4 5 % (n =6 ,P <0 .0 5 )。在 - 5 0mV ,Ik1分别降低 5 % (n =6 ,P <0 .0 5 )和35 % (n =6 ,P <0 .0 5 )。在实验电压为 - 12 0mV ,多非利特 1和 10 μmol·L- 1使Ik1降低 19% (n =8,P <0 .0 5 )及 2 5 % (n =8,P <0 .0 5 )。在 - 5 0mV ,Ik1分别降低 11%和 19% (n =8,P <0 .0 5 )。在实验电压为 - 12 0mV ,RP5 886 6 1和 10 μmol·L- 1使Ik1分别降低 2 1% (n =8,P <0 .0 5 )和 5 0 % (n =8,P <0 .0 5 )。在 - 5 0mV ,Ik1分别降低 6 % (n =8,P <0 .0 5 )和11% (n =8,P <0 .0 5     

Histamine H1-receptor-mediated modulation of the delayed rectifier K+ current in guinea-pig atrial cells: opposite effects on IKs and IKr

1. Histamine receptor-mediated modulation of the rapid and slow components of the delayed rectifier K+ current (IK) was investigated in enzymatically-dissociated atrial cells of guinea-pigs using the whole cell configuration of the patch clamp technique. 2. Histamine at a concentration of 10 microM enhanced IK recorded during strong depolarization to potentials ranging from +20 to +40 mV and inhibited IK recorded during mild depolarization to potentials ranging from -20 to -10 mV. The increase of IK was more prominent with longer depolarizing pulses, whereas the inhibition of IK was more marked with shorter depolarizing pulses, suggesting that histamine enhances IKs (the slow component of IK) and inhibits IKr (the rapid component of IK). 3. The histamine-induced enhancement of IKs and inhibition of IKr were abolished by 3 microM chlorpheniramine but not by 10 microM cimetidine, suggesting that these opposite effects of histamine on IKr and IKs are mediated by H1-receptors. 4. In the presence of 5 microM E-4031, an IKr blocker, histamine hardly affected IK during mild depolarization although it enhanced IK during strong depolarization in a concentration-dependent manner. Histamine increased IKs with EC50 value of 0.7 microM. In the presence of 300 microM indapamide, an IKs blocker, histamine hardly affected IKs but inhibited IKr in a concentration-dependent manner. Histamine decreased IKr with IC50 value of 0.3 microM. 5. Pretreatment with 100 nM calphostin C or 30 nM staurosporine, protein kinase C inhibitors, abolished the histamine-induced enhancement of IKs, but failed to affect the histamine-induced inhibition of IKr. 6. We conclude that in guinea-pig atrial cells H1-receptor stimulation enhances IKs and inhibits IKr through different intracellular mechanisms.