3,5,4＇-三甲基白藜芦醇对豚鼠心室肌细胞钠电流和钾电流的影响

目的研究3,5,4＇-三甲基白藜芦醇（trans-resveratrol derivative3,5,4＇-trimethoxystilbene,TMS）对豚鼠心室肌细胞钠电流（INa）和钾电流（IK1）的直接作用,探讨其心肌保护作用。方法用全细胞膜片钳技术记录TMS对单个心室肌细胞INa和IK1的作用。结果TMS（10μmol·L^-1）可快速抑制豚鼠心室肌细胞INa,用药后3min左右即开始起效,10min时抑制率为（36.8±5.6）%（P〈0.005）,洗脱后可完全恢复;1,3μmol·L^-1TMS未影响INa大小。TMS不改变INa的最大激活电压,也不影响IK1的大小。10μmol·L-1使半数最大失活电压（V1/2）由（-87.0±3.3）mV变化到（-96.7±3.5）mV（P〈0.001）,使失活曲线斜率（S）由（4.9±0.3）mV变化到（5.4±0.3）mV（P〈0.01）;使半数最大激活电压（V1/2）（-38.9±1.4）mV变化到（-47.3±1.3）mV（P〈0.001）,未改变激活S。结论TMS可直接作用于豚鼠心室肌细胞,快速抑制INa,且此作用快速、可逆。     

白藜芦醇对豚鼠心室肌细胞钠电流的影响

目的 研究白藜芦醇(resveratrol,RES)对豚鼠心室肌细胞钠电流(INa)的影响,探讨其心肌保护机制.方法 用全细胞膜片钳技术记录RES对单个心室肌细胞INa的作用.结果 RES(10,30,100 μmol·L-1)浓度依赖性的抑制豚鼠心室肌细胞INa,其中30 μmol·L-1对INa的抑制率为(17.3±3.1)%(P<0.005),100 μmol·L-1抑制率(52.7±10.2)%(P<0.01),抑制作用迅速,用药后3 min左右即开始起效,洗脱后均可以完全恢复;100 μmol·L-1使半数最大失活电压(V1/2)由(-89.3±2.0)mV变化到(-100.7±3.3)mV(P<0.005),RES未改变S和半数最大激活电压(V1/2).结论 RES浓度依赖性的抑制INa,作用出现快,并且可逆.     

葡萄糖对豚鼠心室肌细胞跨膜离子电流的影响

目的观察葡萄糖对豚鼠心室肌细胞膜APD,IK1,IK,ICa-L的影响.方法采用全细胞膜片技术记录单个豚鼠心室肌细胞膜的动作电位时程和离子电流.比较0、10和20mmol·L-1葡萄糖对心室肌细胞跨膜离子电流的作用.结果(1)与10 mmol·L-1葡萄糖相比,0和20mmol·L-1均可使豚鼠心室肌细胞的APD缩短(P＜0.05);(2)在细胞外葡萄糖浓度为10 mmol·L-1时,内向整流钾电流IK1的电流密度最大,标准化I-V曲线显示0和20mmol·L-1葡萄糖均可抑制IK1,并使I-V曲线左移,其翻转电位从-72.4移至-64.6 mV;(3)与mmol·L-1葡萄糖相比,0和20mmol·L-1葡萄糖均可增加ICa-L的电流幅度和电流密度.当钳制电位为10 mV,细胞外葡萄糖浓度为0 mmol·L-1时,ICa-L的电流密度为(-8.03±0.82)pA/pF(n=8),而10mmol·L-1和20mmol·L-1葡萄糖分别使电流密度增加为(-5.45±0.67)pA/pF和(-6.50±0.56)pA/pF;(4)当钳制电压为 70mV,细胞外葡萄糖浓度为0、10和20 mmol·L-1时,IK的电流密度分别为(18.96±2.86)pA/pF,(8.66±1.87)pA/pF,(15.32±3.12)pA/pF.结论细胞外不同浓度的葡萄糖可使豚鼠心室肌细胞APD,IK1,IK,ICa-L发生改变.细胞外葡萄糖浓度为0和20mmol·L-1对细胞膜离子电流产生相似的影响.     

双苯氟嗪对豚鼠心室肌细胞L-钙电流的影响

目的:观察双苯氟嗪(Dip)对豚鼠心室肌细胞L-型钙电流(I_(Ca-L))的影响。方法:酶解法制备单个心室肌细胞。应用全细胞膜片箝技术记录豚鼠单个心室肌细胞钙电流。结果:在0.3-30μmol/L范围内,Dip可浓度依赖性地降低电压依赖性激活I_(Ca-L)峰值,被Dip 3μmol/L所抑制的I_(Ca-L)在冲洗5min后可得到部份恢复。但Dip对I_(Ca-L)的电压依赖特征,最大激活电压,以及I_(Ca-L)稳态激活无明显影响。在Dip3μmol/L存在下,半数激活电压(V_(0.5))和斜率参数(к)与对照组相比,差异均无显著性。V_(0.5)分别为(-12.8±1.7)mV和(-13.2±2.4)mV,к分别为(7.1±0.4)mV和(7.5±0.5)mV(P>0.05)。Dip3μmol/L可明显使钙电流稳态失活曲线左移,加速钙通道电压依赖性稳态失活。V_(0.5)分别为(-19.7±2.4)mV和(-31±6)mV,к分别为(3.6±0.3)mV和(1.8±0.2)mV(P<0.05).Dip 3μmol/L还使I_(Ca-L)从失活状态下的恢复明显减慢。结论:Dip主要作用于L-型钙通道的失活状态,加速钙通道失活,并使其从失活状态下恢复减慢,从而抑制I_(Ca-L)。     

3, 5, 4'-三甲基白藜芦醇对豚鼠心室肌细胞钠电流和钾电流的影响

目的 研究3, 5, 4'-三甲基白藜芦醇(trans-resveratrol derivative 3,5,4'-trimethoxystilbene,TMS)对豚鼠心室肌细胞钠电流(I_Na)和钾电流(I_K1)的直接作用,探讨其心肌保护作用。方法 用全细胞膜片钳技术记录TMS对单个心室肌细胞I_Na和I_K1的作用。结果 TMS(10 μmol·L^-1)可快速抑制豚鼠心室肌细胞I_Na,用药后3 min左右即开始起效,10 min时抑制率为(36.8±5.6)％(P<0.005),洗脱后可完全恢复;1,3 μmol·L^-1 TMS未影响I_Na大小。TMS不改变I_Na的最大激活电压,也不影响I_K1的大小。10 μmol·L^-1使半数最大失活电压(V_1/2)由(-87.0±3.3)mV变化到(-96.7±3.5)mV (P<0.001),使失活曲线斜率(S)由(4.9±0.3)mV 变化到(5.4±0.3)mV (P<0.01);使半数最大激活电压(V_1/2) (-38.9±1.4)mV 变化到(-47.3±1.3)mV (P<0.001),未改变激活S。结论 TMS可直接作用于豚鼠心室肌细胞,快速抑制I_Na,且此作用快速、可逆。     

过氧化氢对大鼠心室肌细胞L-型钙通道电流的影响

目的:研究过氧化氢(H2O2)对单个大鼠心室肌细胞L-型钙通道电流(Ica,L)的影响。方法:用急性酶解法获得单个大鼠心室肌细胞;用标准的全细胞膜片钳技术记录钙通道电流,观察5mmol·L-1H2O2引起单个大鼠心室肌细胞Ica,L改变。结果:在5mmol·L-1H2O2作用下,大鼠心室肌细胞Ica,L峰值电流密度从4.89±0.52pA/pF增加至9.80±0.65pA/pF(P<0.05,n=10),电流-电压曲线下移,但激活电位、峰电位和翻转电位无明显改变;H2O2对Ica,L激活时间常数-电压曲线无明显影响,但可使其灭活时间常数-电压曲线明显向上移;H2O2对Ica,L稳态激活曲线无明显改变,但可使其稳态失活曲线明显左移,V0.5从(-26.85±5.3)mV左移至(-37.20±4.5)mV(P<0.05,n=5)。结论:H2O2可以增加大鼠心肌细胞Ica,L,且使其失活明显减慢。     

氟康唑对豚鼠心室肌细胞I_K和在HEK-293细胞中表达的HERG钾通道的抑制作用

目的研究氟康唑对豚鼠心室肌细胞延迟整流钾电流(IK)和在HEK-293细胞中表达的HERG钾通道的抑制作用。方法应用酶解法消化豚鼠单个心室肌细胞,观察氟康唑对IK的影响;采用磷酸钙沉淀瞬时转染的方法将HERG基因表达于HEK-293细胞上,观察氟康唑对野生型HERG钾通道电流、激活和失活曲线的影响,以及氟康唑对Y652A和F656C突变型HERG钾通道的作用;IK和HERG电流的记录均采用全细胞膜片钳技术。结果氟康唑(0.01、0.1、1、3、10、30、100、300和1 000μmol.L-1)浓度依赖性地抑制IK和HERG钾电流,其IC50值分别为(68.1±21.6)μmol.L-1和(48.2±9.4)μmol.L-1,对HERG钾通道的电压依赖性激活和失活曲线无影响;与野生型(WT)比较,Y652A和F656C突变型可减弱氟康唑对HERG通道的阻断作用。结论氟康唑能阻断IK和HERG通道,Y652和F656是氟康唑与HERG通道结合的关键位点。     

雌二醇抑制豚鼠心室肌细胞内向整流和延迟整流钾通道电流

目的:研究雌二醇(Estradiol,Est)对心室肌细胞动作电位(AP)、内向整流钾通道电流(I_(K1))及延迟整流钾通道电流(I_K)的影响。方法:全细胞膜片箝技术。结果:EST 10μmol·L~(-1)使豚鼠心室肌细胞AP时程明显缩短,APD_(50)由给药前(474±71)ms缩短至(330±75)ms(P<0.05),Est 100μmol·L~(-1)使APD_(50)缩短至(229±67)ms(P<0.01),使APD_(90)由(587±60)ms缩短至(418±79)ms(P<0.05)。Est浓度依赖性地抑制I_K尾电流(I_K·tail),10μmol·L~(-1)浓度下,I_K·tail减少53％(P<0.05),100μmol·L~(-1)浓度下,I_K·tail减少80％(P<0.05)。10μmol·L~(-1)以上浓度Est明显抑制I_(K1),在-100mV刺激电压下,内向电流最大抑制为49％(P<0.01);在-40mV刺激电压下,外向电流最大抑制为72％(P<0.01)。同时,Est使I_(K1)翻转电位向负电位方向移位(由-70mV变为-76mV)。结论:Est对豚鼠心室肌细胞I_(K1)和I_K通道具有明显的抑制作用。     

牛磺酸镁对豚鼠心室肌细胞钾离子通道的影响

目的研究牛磺酸镁(taurine magnesium coordination compound,TMC)对正常豚鼠心室肌细胞钾电流的影响,旨在探讨TMC抗心律失常的作用机制。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豚鼠单个心室肌细胞IK、IK1的影响。结果应用200μmol·L-1TMC使豚鼠单个心室肌细胞IK在实验电压+70mV时,从给药前(8.67±1.04)pA/pF减少到(6.31±1.16)pA/pF(n=5,P<0.01);TMC对IK1无影响。结论本实验表明TMC具有直接抑制心室肌细胞IK作用,减少IK可能会使动作电位时程(APD)和有效不应期(ERP)延长,这可能是其发挥抗心律失常作用的基础之一。     

花生四烯酸乙醇胺对大鼠心肌细胞L型钙电流的影响

目的研究anandamide(花生四烯酸乙醇胺)对单个大鼠心肌细胞L型钙电流(I Ca-L)的影响。方法应用全细胞膜片钳技术记录I Ca-L,并观察anandamide对该电流的作用。结果 (1)anandamide浓度依赖性地减小I Ca-L,其IC50值为(1.3±0.3)μmol·L-1。(2)1μmol·L-1anandamide可明显使稳态失活曲线左移,失活中点电压(V1/2)由(-34.4±0.2)mV变为(-42.2±0.6)mV,K值由(5.7±0.2)变为(6.4±0.4),表明anandamide改变了钙通道失活的电压依赖性。anandamide 1μmol·L-1对稳态激活曲线无明显影响。结论 anandamide可使稳态失活曲线左移而剂量依赖性地减小I Ca-L。     

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。     

Electrophysiological mechanisms of sophocarpine as a potential antiarrhythmic agent

Aim:

To examine the electrophysiological effects of sophocarpine on action potentials (AP) and ionic currents of cardiac myocytes and to compare some of these effects with those of amiodarone.

Methods:

Langendorff perfusion set-up was used in isolated guinea pig heart, and responses to sophocarpine were monitored using electrocardiograph. Conventional microelectrode, voltage clamp technique and perforated patch were employed to record fast response AP (fAP), slow response AP (sAP) and ionic currents in guinea pig papillary muscle or rabbit sinus node cells.

Results:

Tachyarrhythmia produced by isoprenaline (15 μmol/L) could be reversed by sophocarpine (300 μmol/L). Sophocarpine (10 μmol/L) decreased the amplitude by 4.0%, maximal depolarization velocity (V_max) of the fAP by 24.4%, and Na⁺ current (I_Na) by 18.0%, while it prolonged the effective refractory period (ERP) by 21.1%. The same concentration of sophocarpine could also decrease the amplitude and V_max of the sAP, by 26.8% and 25.7%, respectively, and attenuated the Ca²⁺ current (I_CaL) and the K⁺ tail current substantially. Comparison of sophocarpine with amiodarone demonstrated that both prolonged the duration and the ERP of fAP and sAP, both decreased the amplitude and V_max of the fAP and sAP, and both slowed the automatic heart rate.

Conclusion:

Sophocarpine could reverse isoprenaline-induced arrhythmia and inhibit I_Na, I_CaL, and I_Kr currents. The electrophysiological effects of sophocarpine are similar to those of amiodarone, which might be regarded as a prospective antiarrhythmic agent.     

7－溴化乙氧苯四氢巴马汀抑制外向钾电流和尾电流

应用膜片钳封接技术，对中药改构物７－溴化乙氧苯四氢巴马汀（ＥＢＰ）抗心律失常作用机理进行了研究。发现ＥＢＰ明显抑制了豚鼠单个细胞的延迟外向钾电流（ＩＫ）和外向尾电流，这一作用亦具浓度和频率依赖性，ＥＢＰ１０μｍｏｌ·Ｌ－１使ＩＫ从给药前的０．８８ｎＡ减少到０．６７ｎＡ，使尾电流从给药前的０．３６０ｎＡ减少到０．１１０ｎＡ。在膜电位－２０ｍＶ到＋６０ｍＶ区间作用较强。ＥＢＰ对ＩＫ１和钙电流影响不显著。揭示该药抗心律失常主要机理为抑制电压依赖性外向钾电流和尾电流。     

Effectiveness of nalbuphine,a κ-opioid receptor agonist and μ-opioid receptor antagonist,in the inhibition of INa,IK(M), and IK(erg) unlinked to interaction with opioid receptors

Nalbuphine (NAL) is recognized as a mixer with the κ-opioid receptor agonist and the μ-opioid receptor antagonist. However, whether this drug causes any modifications in neuronal ionic currents is unclear. The effects of NAL on ionic currents in mHippoE-14 hippocampal neurons were investigated. In the whole-cell current recordings, NAL suppressed the peak amplitude of voltage-gated Na⁺ current (I_Na) with an IC₅₀ value of 1.9 μM. It shifted the steady-state inactivation curve of peak I_Na to the hyperpolarized potential, suggesting that there is the voltage dependence of NAL-mediated inhibition of peak I_Na. In continued presence of NAL, subsequent application of either dynorphin A_1-13 (1 μM) or naloxone (30 μM) failed to modify its suppression of peak I_Na. Tefluthrin (Tef; 10 μM), a pyrethroid known to activate I_Na, increased peak I_Na with slowed current inactivation; however, further application of NAL suppressed Tef-mediated suppression of peak I_Na followed by an additional slowing of current inactivation. In addition, NAL suppressed the amplitude of M-type K⁺ current [I_K(M)] with an IC₅₀ value of 5.7 μM, while it slightly suppressed erg-mediated and delayed-rectifier K⁺ currents. In the inside-out current recordings, NAL failed to modify the activity of large-conductance Ca²⁺-activated K⁺ channels. In differentiated NG108-15 neuronal cells, NAL also suppressed the peak I_Na, and subsequent addition of Tef reversed NAL-induced suppression of I_Na. Our study highlights the evidence that in addition to modulate opioid receptors, NAL has the propensity to interfere with ionic currents including I_Na and I_K(M), thereby influencing the functional activities of central neurons.     

体外培养海马神经干细胞分化前后离子通道检测

目的:研究神经干细胞(NSCs)分化前后电压依赖性Na 、K 、Ca2 通道的变化。方法:应用全细胞膜片钳技术检测NSCs分化前及分化后3d、7d、14d、21d电压依赖性Na 电流(INa)、延迟整流性K 电流(IK)、电压依赖性Ca2 电流(ICa)。结果: 分化前后均未检出INa,分化前未检出IK,分化后3d、7d、14d、21d,IK检出率分别为11.76%、24.75%、46.51%、76.18%,ICa在分化前后均可检出,分化前和分化后各时间点ICa的幅度分别为(119±73)pA、(213±98)pA、(324±151)pA、(735±312)pA、(1079±307)pA。结论:分化前后均未检出INa,随分化时间延长,IK检出率逐渐增加,ICa幅度逐渐增高。     

Risperidone prolongs cardiac action potential through reduction of K+ currents in rabbit myocytes

Prolongation of QT interval by antipsychotic drugs is an unwanted side effect that may lead to ventricular arrhythmias. The antipsychotic agent risperidone has been shown to cause QT prolongation, especially in case of overdosage. We investigated risperidone effects on action potentials recorded from rabbit Purkinje fibers and ventricular myocardium and on potassium currents recorded from atrial and ventricular rabbit isolated myocytes. The results showed that (1) risperidone (0.1-3 microM) exerted potent lengthening effects on action potential duration in both tissues with higher potency in Purkinje fibers and caused the development of early afterdepolarizations at low stimulation rate; (2) risperidone (0.03-0.3 microM) reduced significantly the current density of the delayed rectifier current and at 30 microM decreased the transient outward and the inward rectifier currents. This study might explain QT prolongation observed in some patients treated with risperidone and gives enlightenment on the risk of cardiac adverse events.     

Further characterization of the effects of imipramine on plateau membrane currents in guinea-pig ventricular myocytes

Summary The effects of imipramine, a tricyclic antidepressant, on action potential characteristics and plateau membrane currents were studied in isolated guineapig ventricular myocytes, using the whole cell configuration of the patch-clamp technique. Imipramine (1, 5 and 15 mol/l) decreased in a concentration-dependent manner the amplitude and shortened the duration of the action potential, but it had no effect on resting membrane potential. At all three concentrations tested, imipramine decreased the delayed outward potassium current, this effect being apparently voltage-independent since it did not modify the activation curve. Imipramine, 5 and 15 mol/l, also produced an inhibition of the peak high threshold calcium current, but did not change the shape of the current-voltage relationship or the apparent reversal potential of this current. Therefore, imipramine probably decreased the maximum available calcium conductance. However, the inward rectifying potassium current was not affected by any concentration of imipramine tested. Imipramine, 1 and 5 mol/l, shortened the duration of the action potentials elicited in the presence of the inorganic calcium channel blocker cobalt chloride, and at 5, but not at 1 mol/l, also shortened the action potentials obtained in the presence of the sodium channel blocker tetrodotoxin. Washout of imipramine completely reversed all its effects within 15 minutes. All these results suggest that imipramine at a concentration of 1 mol/l produced a shortening in action potential duration by inhibiting the late sodium current flowing during the plateau phase of the action potential. At concentrations of 5 and 15 mol/l the effect of imipramine on action potential duration can also be explained by a blocking effect on the high threshold calcium current. Send offprint requests to E. Delpón at the above address     

The p42/44mitogen-activated protein kinase inhibitor PD 98059, but not U 0126, increases a K+ current in cardiomyocytes

1. The effects of the mitogen-activated protein kinase (MAPK) inhibitors PD 98059 and U 0126, useful tools to investigate MAPK involvement in intracellular signal transduction pathways, were assessed on cardiomyocytes. 2. In rat freshly isolated ventricular myocytes, under current-clamp conditions, PD 98059 (40 micro mol/L) shortened the action potential. Under whole-cell patch-clamp, this compound slowly induced a fast activating sustained outward K+ current that was sensitive to 1 mmol/L Ba2+, 100 micro mol/L Gd3+, 3 mmol/L 4-aminopyridine and 100 micro mol/L tetracain. The PD 98059-induced current was prevented by 40 micro mol/L AACOCF3, a cytosolic phospholipase A2 inhibitor. 3. U 0126 (1 micro mol/L), a recently developed highly potent p42/44 MAPK inhibitor, did not alter K+ currents. 4. PD 98059, but not U 0126, increased arachidonic acid content, probably as a consequence of its reported cyclo-oxygenase inhibitory effect. 5. These observations indicate that PD 98059 activates a TREK-1 like current. Thus, this MAPK inhibitor has to be used with caution because alterations in cell metabolism can be secondary to changes in electrophysiological behaviour.     

Inhibition of voltage-gated channel currents in rat auditory cortex neurons by salicylate

Salicylate is a medicine for anti-inflammation with a side effect of tinnitus. To understand the mechanisms of tinnitus induced by salicylate, we studied the effects of salicylate on voltage-gated ion channels and action potential firing rates in freshly dissociated rat pyramidal neurons in auditory cortex (AC) using the whole-cell patch technique. We found that salicylate reduced the voltage-gated sodium current (I(Na)), the delayed rectifier potassium current (I(K(DR))) and the L-type voltage-gated calcium current (I(Ca,L)) in concentration-dependent manner. An amount of 1mM salicylate shifted the steady-state inactivation curve of I(Na) negatively by about 5mV, shifted the steady-state activation and inactivation curve of I(K(DR)) negatively by approximately 14mV and 17mV, respectively, and shifted the steady-state activation curve of I(Ca,L) negatively by about 10mV. 1mM salicylate significantly increased the action potential firing rates, ultimately. From the results, we speculated that through affecting the voltage-gated ion channels in AC, an important position in auditory system, salicylate increased the firing rate of neurons and enhanced neuronal excitability on the one hand, increased the excitatory transmitters release and reduced the inhibitory transmitter release on the other hand, thus finally induced tinnitus.