小鼠心房肌细胞分离和电生理功能鉴定

目的建立小鼠心房肌细胞分离技术,评价心房肌细胞的质量和电生理特性。方法通过改良Bustamante等人所建立的分离人心房肌细胞的方法,分离成年小鼠单个心房肌细胞。台盼蓝染色判定心房肌细胞活性。全细胞膜片钳技术记录细胞膜钾电流,证实细胞的电生理特性。结果分离出的小鼠心房肌细胞呈梭状、横纹清晰、两端边缘锐利、遮光性较强、细胞无明显搏动。全细胞膜片钳记录细胞膜钾电流（Ito,Ikur,Ik1）,证实所分离的心房肌细胞具有典型的钾电流特征。结论 Bustamante法经改良后可以成功地获得适合做电生理需要的单个小鼠心房肌细胞,且易于操作,重现性好。     

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。     

胺碘酮抗心律失常的临床应用（I）

1胺碘酮有哪些电生理作用和药理作用？ 胺碘酮是目前最常用的抗心律失常药物之一，属于Ⅲ类抗心律失常药物，是以Ⅲ类药物为主的心脏离子多通道阻滞剂。胺碘酮能使心房和心室的心肌纤维动作电位时程延长，由此阻滞慢、快成分的延迟整流钾电流（Iks、Ikr），特别是开放状态的Iks。     

坎地沙坦对豚鼠心房肌细胞钾通道电流的影响

目的研究坎地沙坦对正常豚鼠心房肌细胞内向整流钾电流（Ikl）和延迟整流钾电流（Ik）的影响，旨在为临床上应用坎地沙坦预防房颤发作和复发提供理论依据。方法酶解法分离豚鼠单个心房肌细胞，应用全细胞膜片嵌技术，在不同嵌制条件下，记录并分析坎地沙坦对豚鼠单个心房肌细胞Ikl及Ik的影响。结果坎地沙坦对Ikl无影响，但可明显抑制Ik。结论坎地沙坦抑制Ik，使动作电位时程（APD）和有效不应期（ERP）延长，改善房颤电重构及它的现在已明确的抑制结构重构的作用共同参与房颤发作和复发预防的机制。     

多非利特与Chromanol293B对豚鼠心室乳头肌动作电位的影响

目的 研究多非利特和Chromanol 293B对豚鼠乳头肌动作电位的作用,探讨快速延迟整流钾通道(Ikr)和慢速延迟整流钾通道(Iks)电流抗心律失常的作用机制.方法 用标准玻璃微电极技术记录豚鼠乳头肌的动作电位,观察不同刺激频率下动作电位各参数的变化.结果 多非利特能浓度依赖性地延长动作电位的时程,随着刺激频率的增...     

IQ_(23)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(英)

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：IQ_23在10，30，100μmol·L~-皇呈浓度依赖性的减慢AP复极，APD_90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，IQ_23对其两种成分，即I_ks和I_kr，都有阻断作用，30和100mol·L-1IQ_23阻断I_ks达21％和26％，对Ikr为67％和86％。即使在100mol·L-1,IQ_23也不影响内向整流钾电流（Ikl）。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Ca2 无关。1Q23对Iks和Ikr两种成分都有阻断作用，无明显的选择性。     

常咯啉对豚鼠和家兔单个心肌细胞钾电流的影响(英文)

目的:研究常咯啉是否对心肌细胞的钾电流有影响作用。方法:采用高阻抗密封膜片箝全细胞技术,记录分离的豚鼠和家兔心肌单个细胞的钾电流。结果:在临床用量常咯啉50μmol·L~(-1)抑制家兔心房肌细胞的瞬间外向钾电流(I_(TO))17.7％±2.4％(n=8)。但并不影响电压依赖性通道。同一剂量的常咯啉对单个家兔心室肌细胞的内向整流钾电流(I_(Kl))和单个豚鼠心室肌细胞的延迟整流钾电流(I_K)并不产生任何作用。结论:提示常咯啉具有阻制(I_(TO))的作用,而对(I_K)和(I_(Kl))无任何作用。     

N-甲基小檗胺对人心房肌细胞瞬时外向钾电流和延迟整流钾电流的作用(英文)

目的　动物实验表明N 甲基小檗胺 (NMB)通过抑制豚鼠心室肌细胞ATP敏感性钾电流和钙电流来发挥抗心律失常和抗心肌缺血作用 ,故进一步研究NMB对人心肌细胞电流的作用。方法　膜片钳制技术全细胞记录模式研究NMB对人心房肌细胞瞬时外向钾电流 (Ito)和延迟整流钾电流 (IK)的作用。结果　指令电位为 +60mV时 ,NMB 0 .1 ,1 ,1 0 μmol·L-1 分别使Ito幅值下降 (1 6± 4) % ,(2 5±4) %和 (49± 3) % ,使IK 幅值下降 (42± 6) % ,(47±7) %和(65± 3) %。结论　NMB对人心房肌细胞Ito和IK 均有抑制作用。     

小檗碱对腹主动脉狭窄性心肌病大鼠心肌细胞钾电流的抑制作用

目的：研究小檗碱对腹主动脉狭窄性心肌病模型大鼠的心肌细胞中瞬时外向钾电流（Ito）和内向整流钾电流（IK1）的抑制作用,并探讨其作用机制。方法：对大鼠进行腹主动脉狭窄手术建立心肌病模型,以急性酶解法分离大鼠单个左心室肌细胞,用全细胞膜片钳技术记录钾电流。结果：相比于假手术组,心肌病模型组大鼠心肌细胞Ito和IK1的电流密度明显增加;小檗碱（10～100μmol.L-1）可浓度依赖性降低模型组大鼠心肌细胞Ito电流密度,IC50为（43.61±4.31）μmol.L-1,并使Ito稳态失活曲线向负电位方向移动,半数失活电压减少,而对Ito稳态激活曲线和Ito失活后恢复曲线无明显影响;此外,小檗碱可显著降低模型组大鼠心肌细胞IK1电流密度。结论：小檗碱对腹主动脉狭窄所致心肌病中出现异常增大的Ito和IK1离子流有明显阻断作用。     

延胡索乙素对豚鼠单个心室肌细胞钾离子通道的影响

目的研究延胡索乙素(dltetrahydropalmatine,THP)对正常豚鼠心室肌细胞钾电流的影响,旨在探讨延胡索乙素抗心律失常作用机制。方法酶解法分离豚鼠单个心室肌细胞,应用全细胞膜片钳技术记录延胡索乙素对豚鼠单个心室肌细胞钾电流的影响。结果延胡索乙素可明显抑制延迟整流钾电流(IK)和内向整流钾电流(IK1),并呈剂量依赖性。结论延胡索乙素抗心律失常作用机制可能与它对心肌细胞钾通道作用有关,THP可抑制IK和IK1,使动作电位时程(APD)和有效不应期(ERP)延长从而发挥其抗心律失常作用。     

甲状腺素诱导的豚鼠肥厚心肌中延迟整流钾电流离子通道特征

目的在甲状腺素诱导的豚鼠心肌肥厚模型上,研究肥厚心肌细胞延迟整流钾电流（ＩＫ）中快激活成份（Ｉｋｒ）及慢激活成份（Ｉｋｓ）离子通道特征。方法采用全细胞膜片钳技术。结果在甲状腺素诱导的肥厚心肌细胞中,Ｉｋｒ及Ｉｋｓ的电流幅度随去极化电压的增加较正常心肌细胞明显增大,且Ｉｋｒ　ｔａｉｌ及Ｉｋｓ的增加程度分别大于Ｉｋｒ及Ｉｋｓｔａｉｌ°心肌肥厚使Ｉｋｓ激活曲线向负的电压方向偏移,对Ｉｋｒ激活曲线无明显影响。结论甲状腺素诱导的肥厚心肌使Ｉｋｒ及Ｉｋｓ明显增加。     

Effects of propafenone on K currents in human atrial myocytes

1. The class Ic anti-arrhythmic agent, flecainide is known to inhibit the transient outward K current (Ito) selectively in human atrium. We studied the effects of propafenone, another class Ic antiarrhythmic agent, on K currents in human atrial myocytes using a whole-cell voltage-clamp method. 2. Propafenone inhibited both Ito and the sustained or ultra-rapid delayed rectifier K current (Isus or Ikur) evoked by depolarization pulses. The concentration for half-maximal inhibition (IC50) was 4.9 microM for Ito and 8.6 microM for Isus. Propafenone blocked Ito and Isus in a voltage- and use-independent fashion and accelerated the inactivation time constant of Ito [from 28.3 to 6.7 ms at 10 microM propafenone]. 3. The steady-state inactivation curve for Ito was unaffected by propafenone. Propafenone did not affect the initial current at depolarizing potentials, but it did produce a block that increased as a function of time after depolarization (time constant of 3.4 ms). This suggests that propafenone preferentially blocked Ito in the open state. 4. Propafenone had no significant effect on the rate at which Ito recovered from inactivation at -80 mV suggesting that propafenone dissociates rapidly from the channel. 5. The steady-state activation curve for Isus was not affected by propafenone. Propafenone slowed the time course of the onset of the Isus tail current. This suggests that propafenone blocked Isus in the open state. 6. The present results suggest that, unlike flecainide, propafenone blocks both Ito and Isus in human atrial myocytes in the open state at clinically relevant concentrations.     

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.     

Effects of the antifungal antibiotic clotrimazole on human cardiac repolarization potassium currents

The antifungal antibiotic clotrimazole (CLT) shows therapeutic effects on cancer, sickle cell disease, malaria, etc. by inhibiting membrane intermediate-conductance Ca2+ -activated K+ channels (IKCa). However, it is unclear whether this drug would affect human cardiac K+ currents. The present study was therefore designed to investigate the effects of CLT on transient outward K+ current (Ito1), and ultra-rapid delayed rectifier K+ current (IKur) in isolated human atrial myocytes, and cloned hERG channel current (IhERG) and recombinant human cardiac KCNQ1/KCNE1 channel current (IKs) expressed in HEK 293 cells. It was found that CLT inhibited Ito1 with an IC50 of 29.5 microM, accelerated Ito1 inactivation, and decreased recovery of Ito1 from inactivation. In addition, CLT inhibited human atrial I(Kur) in a concentration-dependent manner (IC50 = 7.6 microM). CLT substantially suppressed IhERG (IC50 = 3.6 microM), and negatively shifted the activation conductance of IhERG. Moreover, CLT inhibited IKs (IC50 = 15.1 microM), and positively shifted the activation conductance of the current. These results indicate that the antifungal antibiotic CLT substantially inhibits human cardiac repolarization K+ currents including Ito1, IKur, IhERG, and IKs. However, caution is recommended when correlating the observed in vitro effects on cardiac ion currents to the clinical relevance.     

充血性心衰病人心房肌细胞瞬间外向钾电流和超快速延迟整流钾电流的特征

AIM: To study the properties of transient outward K+ current (Ito) and ultra-rapid delayed rectifier K+ current (IKur) in isolated human atrial myocytes from patients with congestive heart failure (CHF). METHODS: Single cells were isolated from CHF patients with collagenase and protease. Ito and IKur were recorded using whole cell patch-clamp technique. RESULTS: The activation and inactivation of I(to) were voltage-dependent and time-dependent. The half-activation and half-inactivation voltage were (15 +/- 12) mV and (-45 +/- 4) mV respectively. When membrane potential went up from -40 mV to +60 mV, the activation time constant means decreased from (6.9 +/- 2.3) ms to (1.40 +/- 0.20) ms, while the inactivation time constant means decreased from (69 +/- 17) ms to (21 +/- 14) ms. Otherwise, the mean reactivation time constants was (125 +/- 65) ms when the membrane potential was held at -80 mV, but the recovery was not complete during the interval observed. Ito showed less frequency-dependent reduction at test frequency between 0.2-2 Hz. Compared with Ito, the activation of IKur only showed voltage-dependence, without time-dependence. Its mean current densities was (3.4 +/- 0.7) pA/pF when test potential was +60 mV. The half activation voltage of IKur was (23 +/- 14) mV. No clear frequency-dependence was observed at the same frequency range of Ito either. CONCLUSION: I(to) and IKur are important outward potassium channel currents in isolated human atrial myocytes from CHF patients and they have different kinetic properties.     

人心房肌细胞瞬间外向钾电流的特性

目的：研究人的心房肌细胞瞬间外向钾电流（Ｉｔｏ）的特性。方法：采用膜片箝全细胞记录法观察人心房肌通道电流的变化，在用ＣｄＣｌ２ ０．１ｍｍｏｌ·Ｌ＾－１心房肌通道电流的变化，在用ＣｄＣｌ２ ０．１ｍｍｏｌ·Ｌ＾－１阻断钙电流的情况下，细胞膜去极化引出瞬间外向钾电流（Ｉｔｏ）。结果：Ｉｔｏ为电压依赖的电流，迅速激活，迅速失活，４－ＡＰ（４－氨基吡啶）１０ｍｍｏｌ·Ｌ＾－１（选择性的Ｉｔｏ的阻断剂）能     

未成年人心房肌细胞瞬间外向钾电流和内向整流钾电流的特性

AIM: To study the properties of transient outward K+ current (Ito) and inward rectifier K+ current (IKl) in immature human heart. METHODS: Ito and IKl were recorded using whole-cell patch-clamp technique in atrial myocytes isolated from 12 immature (aged from 6 months to 5 a) human hearts. RESULTS: Ito was voltage-dependent, activated and inactivated rapidly. The IC50 (95% confidence limits) of 4-AP on Ito was 0.64 (0.48-0.87) mmol.L-1. 4-AP 1 mmol.L-1 shifted V1/2 of activation from (6.6 +/- 2.0) mV to (19.8 +/- 3.0) mV (n = 4-10, P < 0.01). 4-AP 0.3 mmol.L-1 changed V1/2 of inactivation from (-49 +/- 4) mV to (-61.4 +/- 2.1) mV (n = 3, P < 0.01), but there were no obvious influence on voltage-dependent activation of Ito (P > 0.05). At the same concentration, the recovery time constant (tau value) was prolonged from (108 +/- 16) ms to (220 +/- 67) ms (n = 3-12, P < 0.01). IKl was also voltage-dependent. Its reverse potential was -40 mV. CONCLUSION: Both Ito and IKl are important K+ channel currents in immature human atrial myocytes. 4-AP can affect the inactivation and recovery of Ito at low concentration (0.3 mmol.L-1) and affect its activation at high concentration (1 mmol.L-1).     

Three thiadiazinone derivatives, EMD 60417, EMD 66430, and EMD 66398, with class III antiarrhythmic activity but different electrophysiologic profiles

The thiadiazinone derivatives EMD 60417, EMD 66430, and EMD 66398 were developed as class III antiarrhythmic agents. Their chemical structure is closely related to that of their calcium-sensitizing congener [+]-EMD 60263, and EMD 66398 possesses the methylsulfonylaminobenzoyl moiety present in the prototypical IKr blocker E-4031. We compared the electrophysiologic effects of these compounds with standard drugs (almokalant, E-4031, quinidine) in cardiac myocytes from guinea-pig ventricle and human atrium by whole-cell patch-clamp technique. The test compounds' class III action, which is related to impairment of K+ channel function, was confirmed by action potential measurements. EMD 60417, EMD 66430, EMD 66398, and almokalant (1 microM each) reversibly prolonged the action potential duration in guinea-pig myocytes. In the same cells, the rapidly activating component IKr of the delayed rectifier K+ current, which has been defined by its sensitivity to E-4031, was reduced by EMD 60417, EMD 66430, EMD 66398, and almokalant. Inhibition of IKr was concentration-dependent as determined by attenuation of tail currents. The slowly activating component IKs of the delayed rectifier K+ current was not affected. The inward rectifier K+ current IK1 was not influenced at potentials close to the reversal potential. Transient and sustained outward K+ currents (Ito, Iso) measured in human atrial myocytes were not altered by any EMD compound. L-type Ca2+ current was hardly affected at concentrations of 1-10 microM, but sodium current was decreased. Action potential prolongation by EMD 60417, EMD 66430, and EMD 66398 is due to block of IKr. INa is inhibited at higher concentrations by EMD 66430 and EMD 60417. EMD 66398 is more potent and selective for IKr than EMD 60417 and EMD 66430, and thus resembles E-4031 in structure and function.     

Effects of U50,488H on transient outward and ultra-rapid delayed rectifier K+ currents in young human atrial myocytes

The effects of trans-(+/-)-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)-cyclohexyl]-benzeneacetamide methanesulfonate salt (U50,488H), a selective kappa-opioid receptor agonist, on transient outward K+ current (Ito1) and ultra-rapid delayed rectifier K+ current (IKur) in young human atrial myocytes were evaluated with a whole-cell patch-clamp technique. At +10 mV, U50,488H decreased Ito1 in a concentration-dependent manner (IC50=12.4+/-3.5 microM), while at +50 mV, U50,488H produced biphasic effects on Ito1-increasing and decreasing the current at 1-3 and 10-30 microM, respectively. U50,488H at 10 microM shifted the midpoint (V0.5) of Ito1 activation in a depolarizing direction by approximately 5 mV, accelerated the inactivation, and slowed the recovery from inactivation of Ito1. In addition, U50,488H inhibited IKur in a concentration-dependent manner (IC50=3.3+/-0.6 microM). The effects of U50,488H on the two types of K+ currents were not antagonized by either 5 microM nor-binaltorphimine or 300 nM naloxone. These results indicate that U50,488H affects both Ito1 and IKur in young human atrial myocytes in an opioid receptor-independent manner.