RP58866对哺乳动物心室肌细胞跨膜钾电流的作用(英文)

目的:研究RP58866对于豚鼠或犬分离心室肌细胞I_K,I_(to),和I_(Kl)的影响。方法:采用全细胞膜片箝技术。结果:在-100 mV时,RP58866以浓度依赖方式明显减少了豚鼠心室肌细胞I_(kl),其IC_(50)为(3.4±0.8)μmol·L~(-1)(n=6)。在犬心室肌细胞,RP58866可明显抑制I_(to),其IC_(50)为(2.3±0.5)μmol·L~(-1)。RP58866 100μmol·L~(-1)阻断豚鼠的心室肌细胞I_K,在 40mv时使I_(Kstep)减少(58±13)％,其IC_(50)为(7.5±0.8)μmol·L~(-1),I_(Ktail)减少(86±17)％,其IC_(50)为(3.5±0.9)μmol·L~(-1)。尾电流分析表明,RP58866对I_(Kr)和I_(Ks)均有阻断作用。结论:RP58866对心肌细胞的I_(Kl)和I_(to),I_K均有抑制作用,而不是一种特殊的I_(Kl)抑制剂。     

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。     

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ＩＫ１ ,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ＩＫ１ ,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     

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.     

盐酸非洛普对豚鼠心室肌细胞延迟整流钾电流的抑制作用

目的　已知盐酸非洛普〔1 (2 ,6 二甲基苯氧基 ) 2 (3,4 二甲氧基苯乙氨基 )丙烷盐酸盐 ,DDPH〕对心肌钙电流和钠电流具有抑制作用 ,为全面了解其抗心律失常作用的离子机理 ,研究其对延迟整流钾电流的影响。方法　全细胞膜片钳技术记录豚鼠心室肌细胞快激活的延迟整流钾电流的尾电流(IKr tail)和慢激活的延迟整流钾电流 (IKs)及其尾电流 (IKs tail)。结果　DDPH(1～ 10 0 μmol·L- 1)浓度依赖性地抑制IKr tail,其IC50 为 7.0 (95 %可信限为4 .2 3～ 9.76 ) μmol·L- 1;DDPH 10 μmol·L- 1对IKr tail具有电压依赖性抑制作用。DDPH 10 ,30和 10 0 μmol·L- 1可浓度依赖性地抑制IKs及其IKs tail,使IKs从给药前的 (9.1± 0 .7)pA·pF- 1分别降至 (7.7± 1.7) ,(7.5± 1.8)和 (5 .6± 1.8)pA·pF- 1(P <0 .0 1) ;使IKs tail从给药前的 (1.4± 0 .2 )pA·pF- 1分别降至(1.1± 0 .2 ) ,(0 .9± 0 .2 )和 (0 .6± 0 .2 )pA·pF- 1(P <0 .0 5或P <0 .0 1) ;DDPH 30 μmol·L- 1对IKs tail具有电压依赖性抑制作用。结论　DDPH对豚鼠心室肌细胞延迟整钾电流具有抑制作用。     

苦参碱、小檗胺与胺碘酮、RP58866抗心律失常作用的比较

目的阐明苦参碱和小檗胺抗心律失常作用弱于胺碘酮和RP58866的分子机制。方法采用冠脉结扎、电刺激和乌头碱诱导的心律失常模型观察药物的抗心律失常作用，采用全细胞膜片钳技术测定单个心室肌细胞的I_K1，I_Kr，I_Ks和 I_to。结果苦参碱和小檗胺对冠脉结扎、乌头碱诱发的大鼠心律失常有明显对抗作用，对家兔电刺激致颤阈（VFT）有明显提高作用，但与胺碘酮和RP58866相比，抗心律失常作用明显低于前者。电生理结果显示：苦参碱和小檗胺对家兔I_K1,I_Kr,I_Ks和犬I_to有抑制作用，但较胺碘酮和RP58866作用弱。结论苦参碱和小檗胺的抗心律失常作用及对I_K1,I_Kr,I_Ks和I_to的抑制作用弱于胺碘酮和RP58866。     

IQ23对豚鼠心室肌细胞复极和延迟整流钾电流两种成分的作用

采用膜片钳全细胞记录技术,研究了具有抗心律失常作用的苄基异喹啉衍化物IQ23对豚鼠心室肌单细胞动作电位（AP）和钾电流的作用,结果表明：IQ23在10,30,100umol.L^-1呈浓度依赖性的减慢AP复极,APD90分别延长15％,28％和31％,此效应不依赖细胞外Ca^2 ,电压钳制下记录延迟整流钾电流,IQ23对其两种成分,即Iks和Ikr,都有阻断作用,30和100umol.L^-1 IQ23阻断Iks达21％和26％,对Ikr为67％和86％, 即使在100umol.L^-1IQ23也不影响内向整流钾电流Ik1),本实验表明,IQ23能浓度依赖性的延长心室肌细胞动作电位时程（APD）,此效应与胞外Ca^2 无关;IQ23对Iks和Ikr两种成分都有阻断作用,无明显的选择性。     

抗心律失常药作用机制研究进展

抗心律失常药作用机制研究进展吴跃进（广东医学院药理教研室，湛江５２４０２３）心律失常的产生与持续是心肌电活动紊乱的结果，而电活动则是离子通过离子通道跨膜流动形成的。抗心律失常药主要通过影响心肌电活动而发挥作用，因而以离子通道作为抗心律失常药物作用的靶...     

氯胺酮对豚鼠心室肌细胞中延迟整流钾电流的作用

目的验证并研究局麻药氯胺酮对豚鼠心肌延迟整流钾电流（IK）的作用,并探讨其对心脏功能的影响。方法采用II型胶原酶急性分离豚鼠心室肌细胞,利用全细胞膜片钳技术观察氯胺酮对豚鼠心室肌细胞中IK的作用。结果氯胺酮对心室肌IK有较强的抑制作用,但不影响该类型电流的整流特征。结论临床剂量的氯胺酮可以抑制心肌细胞中的IK,显示氯胺酮有致心律失常之作用,或者具有抗心律失常作用。     

7—溴化乙氧苯四氢巴马汀对豚鼠心室肌细胞电压依赖性通道电流…

目的：研究７－溴化乙氧苯四氢巴马汀（ＥＢＰ）对电压敏感通道电流的影响，方法：在豚鼠心室肌细胞进行全细胞电流钳和电压钳记录，结果：ＥＢＰ３０μｍｏｌ．Ｌ＾－１可使单细胞ＡＰＤ９０从４３０±４７ｍｓ延长至５１４±６１ｍｓ（Ｐ〈０．０５，ｎ＝５）。电压钳研究表明ＥＢＰ可依剂量也抑制１Ｋ及其尾电流，而对１ｋ１，ｌｃａ和ｌＮａ无明显作用，结论：以上结果提示选择性地抑制ｌＫ从而延长动作电位时程，可能是ＥＢＰ抗     

Effects of trimebutine maleate on delayed rectifier K+ currents in guinea-pig ventricular myocytes

The effects of trimebutine maleate, a drug commonly used to regulate motility in the gastrointestinal tract, on the delayed rectifier K+ current (I(K)) were evaluated in guinea-pig ventricular myocytes to determine whether the drug has a proarrhythmic effect through blockade of I(K). Trimebutine decreased I(K) in a concentration-dependent manner. To investigate the effects of trimebutine on two components of I(K) (I(Kr) and I(Ks); rapidly activated and slowly activated components, respectively), we performed the envelope-of-tails test. Trimebutine-sensitive I(K) was determined by digital subtraction of I(K) during exposure to trimebutine from control I(K) for each duration of the test pulse over the range 50 ms-2 s. The ratio of deltaI(K,tail)/deltaI(K) plotted against pulse duration for trimebutine-sensitive I(K) gradually decreased to a steady-state value as the duration of the test pulse was lengthened. This finding suggested a weak inhibitory effect of trimebutine on both I(Kr) and I(Ks). The effects of trimebutine on the inward rectifier K+ current (I(K1)) responsible for the resting potential and final repolarization phase of the action potential were investigated by applying voltage clamp ramps over a broad range of potentials. No significant effects were observed at 10 or 100 microM. We next investigated the effects of the drug on the L-type Ca2+ current (I(Ca)). Significant inhibition of I(Ca) was observed at trimebutine concentrations greater than 10 microM. These results suggested that trimebutine maleate has weak inhibitory effects on I(Kr), I(Ks) and I(Ca) at concentrations much higher than those in clinical use.     

Inactivation block of the HERG human cardiac K+ channels by RP58866.

1. RP58866 possesses a unique electrophysiological property: highly effective against various types of arrhythmias including ventricular fibrillation in animal models, noticeably those occurring during ischaemia with depolarized membrane due to elevated extracellular K+ concentrations. To understand the potential ionic mechanisms, we performed detailed studies on the effects of RP58866 on the HERG channels expressed in Xenopus oocytes, which are believed to be important compositions of the rapid component of delayed rectifier K+ current in the hearts. 2. RP58866 significantly inhibited the HERG channels in a concentration-dependent manner, with approximately 50% decrease in the current amplitude at a concentration of 1 microM. RP58866 produced more pronounced inhibition with voltage protocols which favoured inactivation of the HERG channels. It caused substantial negative shift of the inactivation curves but did not alter the activation properties. The inhibition was considerably relieved by elevating [K+]o from 5 - 20 mM, which weakened the channel inactivation. More importantly, the potency was reduced by approximately 100 fold on the mutated HERG channels (S631A) in which the C-type inactivation was substantially weakened. 4. We conclude that blockade of the HERG channels by RP58866 is mainly associated with the binding of the drugs to the inactivated channels. This unique property of HERG blockade might explain some previously reported but unexplained observations: RP58866 maintains its efficacy in APD prolongation with depolarized membrane potential and in arrhythmias during ischaemia with manifested membrane depolarization.     

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.     

Actions of the anti-oestrogen agent clomiphene on outward K+ currents in rat ventricular myocytes

1. The effects of clomiphene (CLM) on cardiac outward K+ current components from rat isolated ventricular myocytes were investigated using the whole-cell patch-clamp technique. Clomiphene (10 micromol/L) significantly inhibited both peak (Ipeak) and end-pulse (Ilate) outward currents (elicited by a 500 msec voltage step from -40 to +50 mV in the presence of K+-containing intracellular and extracellular solutions) by approximately 37% (n = 6; P < 0.01) and 49% (n = 6; P < 0.01), respectively. In contrast, CLM had no effect on outward currents when K+-free solutions were used. 2. A double-pulse protocol and Boltzmann fitting were used to separate individual K+ current components on the basis of their voltage-dependent inactivation properties. At potentials positive to -80 mV, two inactivating transient outward components (Ito) and (IKx) and a non-inactivating steady state component (Iss) could be distinguished. 3. Clomiphene inhibited both Ito and Iss. The maximal block of Ito and Iss induced by CLM (100 micromol/L) was approximately 61% (n = 5) and 43% (n = 5) with IC50 values of 1.54 +/- 0.39 and 2.2 +/- 0.4 micromol/L, respectively. In contrast, the peak magnitude of IKx was unaltered by CLM, although its time-course of inactivation was accelerated. 4. Further experiments whereby myocytes were superfused with the vasoactive peptide endothelin (ET)-1 (20 nmol/L) revealed that CLM (10 micro mol/L) completely abolished the ET-1-sensitive component of Iss. 5. Our findings demonstrate, for the first time, the effects of CLM on distinct cardiac K+ current components and show that CLM modulates the voltage-gated K+ current components Ito and IKx and inhibits the steady state outward current Iss in rat ventricular myocytes.     

Block of NA+ and K+ currents in rat ventricular myocytes by quinacainol and quinidine

1. The electrophysiological actions of quinacainol were investigated on sodium (I(Na)), transient outward (i(to)) and sustained-outward plateau (iKsus) potassium currents in rat isolated cardiac myocytes using the whole-cell patch-clamp technique and compared with quinidine. 2. Quinacainol blocked sodium currents in a concentration-dependent manner and with a potency similar to that of quinidine (mean (+/-SEM) EC50 50+/-12 vs 95+/-25 micromol/L for quinidine and quinacainol, respectively). However, quinacainol had a considerably prolonged onset and recovery from block compared with quinidine. 3. Neither quinacainol nor quinidine significantly changed the steady state voltage dependence of activation of sodium currents. Quinidine produced a hyperpolarizing shift in the voltage dependence for sodium current inactivation, but no such shift was observed with quinacainol at doses that produced a substantial current block. 4. Although quinacainol did not effectively block voltage-dependent potassium currents, even at concentrations as high as 1.5 mmol/L, quinidine, at a half-maximal sodium channel-blocking concentration, reduced peak i(to) current amplitude, increased the rate of inactivation of i(to) and blocked iKsus. 5. These results indicate that quinacainol, a quinidine analogue, blocks sodium currents in cardiac myocytes with little effect on i(to) or iKsus potassium currents, which suggests that quinacainol may be exerting class 1c anti-arrhythmic actions.     

咪达唑仑对大鼠单一心室肌细胞ATP敏感性钾电流的作用

目的研究咪达唑仑对大鼠单一心室肌细胞ATP敏感性钾电流(IKATP)的作用。方法急性酶解法分离大鼠心室肌细胞,利用膜片钳制技术全细胞记录法,设保持电位为-40mV,指令电位为-100～+40mV,步阶脉冲20mV,波宽200ms,刺激间隔6s的方波钳制方案进行刺激。结果咪达唑仑能够开放心室肌细胞ATP敏感性钾(KATP)通道,在一定范围内具有剂量依赖性关系。指令电位在-60mV时,咪达唑仑(0.3～10μmol/L)可使KATP通道开放率分别增加至给药前的(119±5)%,(121±4)%和(121±6)%(P<0.01,n=9)。更高浓度(50～100μmol/L)咪达唑仑使KATP通道开放率略有下降,其他指令电位下的IKATP改变也符合此趋势。结论咪达唑仑对大鼠单一心室肌细胞KATP通道具有开放作用,这可能是其发挥心脏保护的机制之一。     

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     

Carvedilol blocks the repolarizing K+ currents and the L-type Ca2+ current in rabbit ventricular myocytes.

Carvedilol ((+/-)-1-(carbazol-4-yloxy)-3-[[2-(o-methoxyphenoxy)ethyl]am ino]-2-propanol), a beta-adrenoceptor-blocking agent with vasodilator properties, has been reported to produce dose-related improvements in left ventricular function and reduction in mortality in patients with chronic heart failure. However, its electrophysiological effects have not been elucidated. We studied ion channel and action potential modulation by carvedilol in rabbit ventricular preparations using whole-cell voltage-clamp and standard microelectrode techniques. In ventricular myocytes, carvedilol blocked the rapidly activating component of the delayed rectifier K+ current (I(Kr)) in a concentration-dependent manner (IC50 = 0.35 microM). This block was voltage- and time-independent; a prolongation of the depolarizing pulses from a holding potential of -50 mV to +10 mV within the range of 100-3000 ms did not affect the extent of I(Kr) block. Carvedilol also inhibited the L-type Ca2+ current (I(Ca)), the transient outward K+ current (I(to)) and the slowly activating component of the delayed rectifier K+ current (I(Ks)) with IC50 of 3.59, 3.34, and 12.54 microM, respectively. Carvedilol (0.3-30 microM) had no significant effects on the inward rectifier K+ current. In papillary muscles from rabbits pretreated with reserpine, action potential duration was prolonged by 7-12% with 1 microM and by 12-24% with 3 microM carvedilol at stimulation frequencies of 0.1-3.0 Hz. No further action potential duration prolongation was observed at concentrations higher than 3 microM. These results suggest that concomitant block of K+ and Ca2+ currents by carvedilol resulted in a moderate prolongation of action potential duration with minimal reverse frequency-dependence. Such electrophysiological effects of carvedilol would be beneficial in the treatment of ventricular tachyarrhythmias.     

Effects of NIP-141 on K currents in human atrial myocytes.

A novel benzopyran derivative, NIP-141, effectively terminates experimental atrial fibrillation in canine hearts by prolonging atrial refractoriness. However, the effects of this drug on human atrial myocytes are unknown. This experiment evaluated the effects of NIP-141 on K currents in isolated human atrial myocytes using a whole-cell voltage-clamp method. NIP-141 inhibited the transient outward current (I(to)) and the ultra-rapid delayed rectifier K current (I(Kur)), each in a dose-dependent manner, with half-maximal inhibition concentrations of 16.3 microM and 5.3 microM, respectively (n = 5). NIP-141 inhibited both K currents in a voltage- and use-independent fashion, and it preferentially blocked them in the open state and dissociated rapidly from the channel. Because both K currents contribute significantly to the repolarization of the atrial action potential, these findings suggest that NIP-141 may terminate atrial fibrillation by prolonging action potential duration.