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。     

雌激素对Kv2.1钾电流及大鼠海马神经元延迟整流钾电流的影响

目的研究17β-雌二醇对Kv2.1钾电流和原代培养大鼠海马神经元延迟整流钾电流的作用。方法采用HEK293-Kv2.1细胞培养、大鼠海马神经元原代培养和膜片钳全细胞记录技术。结果17β-雌二醇浓度依赖地抑制Kv2.1钾电流和原代培养大鼠海马神经元延迟整流钾电流(I_K)。17β-雌二醇抑制Kv2.1钾电流和原代培养大鼠海马神经元延迟整流钾电流的IC₅₀分别为2.4和4.0 μmol·L^-1。通道动力学研究发现，17β-雌二醇(3 μmol·L^-1)显著左移Kv2.1钾电流的稳态激活和失活曲线，但只显著左移海马神经元延迟整流钾电流稳态激活曲线，而不影响该电流的稳态失活曲线。结论17β-雌二醇抑制Kv2.1钾电流与抑制I_K的程度相近，17β-雌二醇抑制I_K的作用可能部分通过阻断Kv2.1钾电流而实现。     

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。}     

青蒿素对克隆的内向整流钾通道的抑制作用

采用双电极电压钳技术观测了青蒿素对表达于非洲蛙卵的克隆内向整流钾通道(K_ir2.1)的影响. 当蛙卵注射K_ir2.1 cRNA后灌注不同浓度青蒿素时, 青蒿素呈浓度依赖关系降低K_ir2.1钾通道在非洲蛙卵细胞膜的功能表达. 青蒿素阻断K_ir2.1钾通道亦呈电压依赖性. 当指令电压为-140, -130和-120 mV时, 5和50 μmol·L^-1的青蒿素可使K_ir2.1钾通道的内向电流分别下降14.2%, 34.5%; 12.0%, 24.6%; 4.3%, 19.1%. 当指令电压为-50, -40和-30 mV时, 5和50 μmol·L^-1的青蒿素则使K_ir2.1钾通道的外向电流分别增加22.2%, 72.2%; 28.0%, 80.0%; 24.1%, 69.0%. 青蒿素对K_ir2.1通道的阻断作用在用正常灌注液冲洗后可恢复. 青蒿素的抗心律失常作用与它阻断K_ir2.1通道电流有关.     

慢性孵育β-淀粉样肽(25-35)对培养大鼠海马神经元外向钾电流的影响

目的　研究慢性孵育β-淀粉样肽_(25-35) (β-AP_25-35)对海马神经元上瞬时外向钾电流(I_A)和延迟整流钾电流(I_K)的影响。方法　在培养的大鼠海马神经元上用膜片钳全细胞记录钾通道电流。结果　β-AP_25-35 3μmol·L^-1 孵育细胞24h ,I_K 电流幅度增加(44.3±5.4)% ,电流密度由(30.4±6.4)pA·PF^-1 增加至(43.8±4.7)pA·PF^-1 ;β-AP_25-3510μmol·L^-1 孵育12h ,I_K 电流幅度增加(69.8±4.1) % ,电流密度增加至(51.6±7.9)pA·PF^-1,呈浓度依赖性;β-AP_25-35引起的I_K 增加对TEA 5mmol·L^-1 敏感;β-AP_25-35上调I_K 的作用主要发生在β-AP_25-355用药后48h内。β-AP_25-35对I_A无显著性影响。结论　β-AP_25-35选择性地增加海马神经元上I_K,这一作用可能与β-AP的神经毒性有关     

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     

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。     

妥卡尼对豚鼠心室肌细胞钙电流和钾电流的抑制作用

利用酶分散的成年豚鼠心室肌细胞和全细胞电压钳技术,研究了妥卡尼(tocainide)对心室肌细胞钙电流(I_ca)、延迟整流钾电流(I_k)和ATP敏感性钾电流(Ik,ATP)的作用。结果表明,妥卡尼对I_ca和I_k均显示浓度相关的抑制作用,妥卡尼50umol·L^-1对I_ca和I_k的抑制率分别为16%和3%。这可能是妥卡尼有效抑制室上性心动过速和缩短心肌动作电位平台期的重要机制。     

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。     

苄基四氢巴马汀细胞内用药对豚鼠乳头状肌动作电位和心室肌细胞延迟整流钾电流的作用

目的　研究将苄基四氢巴马汀(BTHP)导入细胞内对豚鼠乳头状肌动作电位及单个心室肌细胞延迟整流钾电流的影响。方法　利用外加电压脉冲将药物导入乳头状肌细胞内，并用标准微电极方法测定动作电位；利用浓度差扩散方式使药物进入单个心室肌细胞内，采用全细胞膜片钳技术记录延迟整流钾电流（I_K）。结果　100 μmol.L^-1 BTHP使APD₂₀和APD₉₀分别延长13.5%和20.5%。30 μmol.L^-1 BTHP使I_K和I_K,tail分别从（14.1±2.2) pA.pF^-1和(4.0±0.6) pA.pF^-1降至(9.4±1.3) pA.pF^-1和(2.1±1.0) pA.pF^-1，下降率分别为33.2%和35.3%。 该药使I_K和I_K,tail的I-V曲线幅度降低，对曲线形状影响不明显。结论　BTHP入细胞内后可阻滞延迟整流钾电流和延长动作电位时程。     

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.     

维司力农对培养鸡胚心室肌细胞内向整流性钾电流的作用

目的研究维司力农对培养鸡胚心室肌细胞内向整流性钾电流（Ik1）的作用。方法采用细胞贴附式膜片钳技术。结果1×10-5mol·L-1维司力农可抑制Ik1通道的稳态电导，同时使斜率电导从28.44pS降至10.77pS，Ik1通道的开放时间常数也缩短。结论维司力农对Ik1具有显著的抑制作用。这一效应可部分解释为何作为强心药的维司力农还同时具有抗心律失常作用。     

Electrophysiological Effects of the Anti‐Cancer Drug Lapatinib on Cardiac Repolarization

Abstract: Lapatinib is one of several tyrosine kinase inhibitors used against solid tumour cancers such as breast and lung cancer. Although lapatinib is associated with a risk of QT prolongation, the effects of the drug on cellular cardiac electrical properties and on action potential duration (APD) have not been studied. To evaluate the potential effects of lapatinib on cardiac repolarization, we investigated its electrophysiological effects using a whole‐cell patch–clamp technique in transiently transfected HEK293 cells expressing human ether‐à‐go‐go (hERG; to examine the rapidly activating delayed rectifier K⁺ current, I_Kr), KCNQ1/KCNE1 (to examine the slowly activating delayed rectifier K⁺ current, I_Ks), KCNJ2 (to examine the inwardly rectifying K⁺ current, I_K1), or SCN5A (to examine the inward Na⁺ current, I_Na) and in rat cardiac myocytes (to examine the inward Ca²⁺ current, I_Ca). We also examined its effects on the APD at 90% (APD₉₀) in isolated rabbit Purkinje fibres. In ion channel studies, lapatinib inhibited the hERG current in a concentration‐dependent manner, with a half‐maximum inhibition concentration (IC₅₀) of 0.8 ± 0.09 μm . In contrast, at concentrations up to 3 μm , lapatinib did not significantly reduce the I_Na, I_K1 or I_Ca amplitudes; at 3 μm , it did slightly inhibit the I_Ks amplitude (by 19.4 ± 4.7%; p < 0.05). At 5 μm , lapatinib induced prolongation of APD₉₀ by 16.1% (p < 0.05). These results suggest that the APD₉₀‐prolonging effect of lapatinib on rabbit Purkinje fibres is primarily a result of inhibition of the hERG current and I_Ks, but not I_Na, I_K1 or I_Ca.     

ELECTROPHYSIOLOGICAL EFFECTS OF CHANGROLIN, AN ANTIARRHYTHMIC AGENT DERIVED FROM DICHROA FEBRIFUGA, ON GUINEA-PIG AND RABBIT HEART CELLS

1. The electrophysiological effects of changrolin (CRL), a Chinese antiarrhythmic drug derived from a traditional anti-malarial plant, were examined using the whole-cell patch-clamp method on single cells isolated from guinea-pig and rabbit hearts. 2. At a clinically relevant concentration of 50μmol/L changrolin inhibited Ic_a. by 19.3 ± 6.0% and 17.3 ± 2.6% in guinea-pig and rabbit ventricular cells, respectively. The voltage-dependent channel availability curve was not affected. The CRL effect was enhanced to a small extent during a repetitive stimulation at 2 Hz. 3. In_a was resistant to CRL and the channel availability curve was also unaffected. A small use-dependent inhibition was observed only when the In_a was elicited at 5 Hz in the presence of 300 μmol/L CRL. 4. At 50 μmol/L, CRL did not affect the time-independent inward rectifier and the delayed rectifier K⁺ currents (Iki and Ik, respectively), but inhibited the transient outward current (Ito) by 17.7 ± 2.4%. Changrolin significantly shortened the action potential duration in both guinea-pig and rabbit ventricular cells. 5. In conclusion, CRL inhibits Ic_a and Ito but has little effect on In_a.     

Antiarrhythmic effects and ionic mechanisms of allicin on myocardial injury of diabetic rats induced by streptozotocin

The aim of this study was to evaluate the antiarrhythmic effect of allicin (AL) on streptozotocin (STZ)-induced diabetic rats and explore the possible mechanisms. Hyperglycemia was induced in rats by single intraperitoneal injection of STZ (40 mg/kg). Three days after STZ treatment, the hyperglycemic rats (plasma glucose levels ≥16.7 mM) were administered with AL (4, 8, and 16 mg/kg) by intraperitoneal injection daily for 28 days. The fasting blood glucose levels were measured on every seventh day during the 28 days of treatment. The body weight and blood glucose levels were detected after 28 days. Antiarrhythmic effect of AL was observed in the diabetic rats induced by BaCl₂. To determine the ionic mechanism in rat ventricular myocytes of AL, action potential duration (APD), L-type calcium current (I_Ca-L), and inward rectifier potassium current (I_K1) were recorded by the whole cell-patch clamp technique. The expressions of L-type calcium channel protein α_1C mRNA and cell potassium channels protein Kir2.1 mRNA were studied by RT-PCR. AL normalized the RR interval and QT interval in diabetic rats. AL obviously delayed the onset of ventricular arrhythmia and reduced the score of arrhythmia induced by BaCl₂. Electrophysiological experiment revealed that AL could shorten APD through inhibition of I_Ca-L and enhancement of I_K1. RT-PCR analysis indicated that long-term treatment with AL could decrease the expression of α_1C mRNA and increase the expression of Kir2.1 mRNA. AL has antiarrhythmic effect in STZ-induced diabetic rats. It is tempting for the application of AL to be a useful therapeutic approach in diabetes with ventricular arrhythmia.     

牛磺酸镁对缺氧/复氧致大鼠心肌细胞内向整流钾通道异常的影响

目的观察牛磺酸镁配合物(taurine magnesium coordi-nation compound,TMCC)对缺氧/复氧损伤所致大鼠心肌细胞异常内向整流钾通道电流(Ik1)的影响。方法采用Lan-gendorff逆行主动脉灌流酶溶液消化法急性分离大鼠单个心肌细胞,在电压钳模式下,应用全细胞膜片钳技术记录不同浓度TMCC对正常细胞和不同浓度TMCC及胺碘酮对缺氧/复氧模型细胞内向整流钾通道电流Ik1的变化。结果不同浓度TMCC对正常大鼠心肌细胞的Ik1无明显性影响。缺氧/复氧能使Ik1内向电流峰值从(-13.05±1.43)pA.pF-1降至(-6.94±0.59)pA.pF-1(n=6,P<0.01),内向电流曲线上移。与缺氧/复氧组相比,TMCC(100、200、400μmol.L-1)可使减小的内向电流峰值分别恢复为(-7.21±0.79)pA.pF-1、(-7.28±0.22)pA.pF-1、(-10.96±0.78)pA.pF-1(n=6,P<0.01),24.24μmol.L-1胺碘酮使其恢复为(-8.80±0.97)pA.pF-1。TMCC(100、200、400μmol.L-1)和胺碘酮均可使上移的内向电流曲线下移。缺氧/复氧使大鼠心肌细胞Ik1外向电流峰值从(2.43±0.32)pA.pF-1降至(1.31±0.28)pA.pF-1,I-V曲线下移。与缺氧/复氧组相比,TMCC(100、200、400μmol.L-1)可使减小的外向电流分别恢复为(0.90±0.14)pA.pF-1、(1.84±0.46)pA.pF-1、(2.36±0.40)pA.pF-1、24.24μmol.L-1胺碘酮使其恢复为(2.16±0.69)pA.pF-1。TMCC(100、200、400μmol.L-1)和胺碘酮均可使下移的外向电流曲线上移。结论 TMCC对正常心肌细胞Ik1无影响,但能恢复缺氧/复氧减小的Ik1内向电流和外向电流峰值。提示TMCC对Ik1的作用可能是其发挥抗心律失常的机制之一。     

粉防己碱对犬心浦氏纤维慢内向电流的作用

应用双微电极电压钳技术,观察粉防己碱(Tet) 对犬心脏浦氏纤维细胞的慢内向电流I_si的影响,发现Tet对I_si的峰值有明显减弱作用。Tet的这种效应呈剂量及时间依赖性。当Tet浓度为30μmol/L和100μmol/L,给药后10min时,I_si的峰值分别由给药前的47.9±5.6 nA和38.4±21.5nA降至21±7.8nA和6.3±7.7nA,P值均小于0.01。Tet100μmol/L对由二价阳离子Sr²⁺所介导的I_si亦有明显的抑制作用。结果提示Tet是一慢通道阻滞剂。     

Electrophysiologic actions of aprindine in rabbit atrioventricular node

Summary Aprindine hydrochloride is a potent antiarrhythmic agent against various atrial and ventricular tachyarrhythmias. To elucidate its pharmacological actions in the atrioventricular node, electrophysiologic experiments were conducted by applying microelectrode and voltage clamp methods to small preparations of the rabbit atrioventricular node.At a concentration 1 mol/l, aprindine decreased the spontaneous firing frequency, maximal rate of depolarization, action potential amplitude, and take-off potential (P < 0.05, n = 7). The spontaneous and rate-controlled action potential durations at 50 and 100% repolarization were prolonged by aprindine. Voltage-clamp experiments using the double microelectrode method revealed that aprindine blocked the slow inward current (I_si) in a voltage-dependent manner with a dissociation constant of 10 mol/l and Hill coefficient of 0.8. The steady-state inactivation curve for I_si was shifted toward more negative potentials by 2.5 ± 0.9 mV (P < 0.05, n = 5) without a significant change in the slope factor. This finding suggests that aprindine has a higher affinity for inactivated slow inward (or Ca²⁺) channels than for resting channels. Aprindine caused use-dependent block of I_si, a result consistent with the drug's slow dissociation from inactivated Ca²⁺ channels. The delayed rectifying K⁺ current (I_K) tail obtained on repolarization from +10 mV to –60 mV was significantly decreased from 15.4 ± 2.4 to 6.8 ± 1.4 nA (P < 0.01, n = 6) and the deactivation time constant significantly increased by 20.7% (P < 0.01, n = 6). The steady-state activation curve for I_K was shifted in the hyperpolarized direction by 6.9 ± 2.9 mV, suggesting a potent voltage-dependent block of this current by aprindine. The hyperpolarization-activated inward current (1_h) was decreased from 14.4 ± 5.4 to 12.0 ± 5.5 nA (P < 0.05, n = 5). The transient outward and inward currents induced by 1 mol/l acetylstrophanthidin were almost completely suppressed after the addition of 1 mol/l aprindine.These results suggest that aprindine exerts a negative chronotropic action both by slowing deactivation of I_K and by reducing Is; and Ih, and delays atrioventricular nodal conduction by reducing Is; and IK. These blocking actions of aprindine together with its inhibition of the transient outward and inward currents may explain its antiarrhythmic effects on the atrioventricular node. Send offprint requests to Yoshio Watanabe at the above address