西洛他唑对人心房肌细胞瞬间外向钾电流的影响

目的:观察西洛他唑对人心房肌细胞瞬间外向钾电流(Ito1)的影响,探讨该药抗心律失常作用的机制.方法:二步酶解法分离人单个右心房肌细胞,应用全细胞膜片钳技术记录人心房肌细胞Ito1.结果:在保持电位-50 mV和去极化脉冲为 50 mV条件下,30 μmol/L西洛他唑显著降低Ito1,使Ito1幅值由加药前(8.16±0.70)pA/pF降至(4.84±0.60)pA/pF(P<0.01).西洛他唑在1～50 μmol/L范围内呈浓度依赖性的抑制Ito1,1 μmol/L时即产生作用,50 μmol/L时达最大效应(降低51.09%±3.00%),IC50为(13.18±2.60)μmol/L.此外,该药对Ito1的电压依赖性激活和失活曲线以及恢复曲线均无显著影响.结论:本实验结果表明西洛他唑浓度依赖性地阻滞人心房肌细胞的Ito1.     

去甲肾上腺素对大鼠肝细胞延迟外向钾电流的影响

目前为止国内外尚未见到有关大鼠肝细胞外向钾电流方面的报道。本文用全细胞膜片宿制技术观察了大鼠肝细胞延迟外向钾电流（Ik）及去甲肾上腺素等对人的影响。实验结果表明,在保持电位-50mV、指令电位＋140mV时大鼠肝细胞Ik为2．85±1.21nA。去甲肾上腺素明显降低IK,异丙肾上腺素和乙酰胆碱对IK无影响。     

Mode of inhibition of transient outward current by 1-benzyl-1,2,3,4-tetrahydroisoquinoline in rat ventricular cells

In this study, we examined the effects of 1-benzyl-1,2,3,4-tetrahydroisoquinoline (S49) on a transient outward current (I_to) in rat ventricular myocytes using the whole-cell patch-clamp technique. Depolarization of ventricular myocytes not only activated I_to, but sustained outward currents as well. S49 dose-dependently inhibited the amplitude or integral of I_to, with a 50% inhibitory concentration (IC₅₀) of 4.3 and 2.7 µM, respectively. The inhibition of I_to by S49 was associated with an acceleration of I_to decay. However, S49 had no effect on half inactivation voltage (V_0.5) and slope factor of the voltage-dependent steady-state inactivation curve of I_to. Time-course analysis revealed that S49 developed a block during the depolarizing voltage-clamp step in a monoexponential manner. The rate and magnitude of block were concentration dependent. The equilibrium dissociation constant (K_d) used to inhibit I_to induced by S49, as calculated from the time constant of developing block, was 3.4 µM. The time constant of recovery of I_to from the inactivation state was prolonged by S49. Following treatment with quinidine, the process of I_to recovery was divided into rapid and extremely slow recovery components. Also, the relief from quinidine- or S49-induced block was assessed by comparing the recovery processes of I_to with or without drugs. That comparison revealed the relief from the block of I_to channels by S49 to be more rapid. In summary, the inhibition of I_to by S49 was dose dependent, time dependent but voltage independent. The mechanisms of action might be an open-state block.     

孤啡肽对大鼠顶叶皮层神经元瞬时外向钾电流的抑制作用

目的：研究孤啡肽（N／OFQ）对大鼠顶叶皮层神经元瞬时外向钾电流（IA）的影响,初步探讨其作用的通道动力学机制。方法：采用全细胞膜片钳技术,观察N／OFQ对急性分离的大鼠顶叶皮层神经元IA的作用。结果：①0．1μmol／L N／OFQ使IA幅值由给药前的（5356．1±361．6）pA下降为（4113．3±312．7）pA,抑制率为23．20％±2．17％（P〈0．01,n=10）。②0．1μmol／L N／OFQ使IA的电流-电压（I-V）曲线降低（P〈0．01,n=10）。③0．1μmol／L N／OFQ使,IA激活曲线的半数激活电压（V1／2）和斜率因子（κ）分别由给药前的（-9．2±2．5）mV和（20．4±2．3）mV变为给药后的（30．6±3．7）mV（P〈0．01,n=8）和（22．6±2．1）mV（P〉0．05,n=8）。④0．1μmol／L N／OFQ使IA失活曲线的半数失活电压（V1／2）和斜率因子（κ）分别由给药前的（-64．1±3．2）mV和（21．5±2．1）mV变为给药后的（-55．9±1．9）mV（P〈0．05,n=5）和（19．6±2．2）mV（P〉0．05,n=5）。结论：N／OFQ可抑制大鼠顶叶皮层神经元IA,使其激活曲线、失活曲线均右移。     

葛根素对大鼠心室肌细胞动作电位及钾通道电流的影响

目的:观察葛根素对大鼠心室肌细胞动作电位及钾通道电流的影响。方法:用常规微电极方法记录大鼠心室肌细胞动作电位,用全细胞膜片钳技术记录游离心室肌细胞钾离子流。结果:不同浓度的葛根素均能延长大鼠心室肌细胞动作电位时程(APD)及抑制内向整流钾电流,具有明显的浓度依赖关系。结论:葛根素延长APD,抑制内向整流钾电流,可能是其抗心律失常的机制。     

Effects of cyhalothrin on the transient outward potassium current in central neurons of Helicoverpa armigera

The effects of cyhalothrin on the transient outward potassium current in central neurons of Helicoverpa armigera were studied by using the patch clamp techniques. The results showed that before using cyhalothrin （10.5 mmol/L）, activation potential was approximately -40 mV, after application of the drug, the activation potential shifted roughly 10 mV to the negative potential direction, so channels can be activated more easily. Before and after cyhalothrin application, the change of current amplitude was insignificant. The value of V1/2 and k of activation curves did not change significantly, however, the V1/2 of the inactivation curves changed significantly. Inactivation curves significantly shifted to a negative direction, so that inactivation of the channels was hastened. It is indicated that there may exit a primary way in which cyhalothrin provides neurotoxicity to the nervous system through the regulation of activation potentials and inactivation state of IA channels.     

Differentiation of potassium currents in cultured inhibitory interneurons of the rat hippocampus (identification of the potassium M-type current)

Using a patch-clamp technique in the whole-cell configuration, we identified the potassium M-type current and estimated its contribution to the integral depolarization-induced potassium current evoked in cultured hippocampal inhibitory interneurons of the rat. With the help of immunocytochemical labeling, we checked the presence of the KCNQ-family channels responsible for generation of M current in these neurons. It was demonstrated that non-inactivated potassium channels and channels with slow kinetics play the main role in the processes of repolarization of the membrane of inhibitory interneurons. In all studied cells, a potassium current non-inactivated with time and possessing kinetic parameters close to those of the M current developed in response to depolarization. In all cells, positive immunocytochemical labeling with respect to KCNQ2 channels was observed; however, its intensity varied significantly from neuron to neuron. The level of suppression of non-inactivated potassium currents by a blocker of KCNQ channels, linopirdine, varied noticeably in different cells; therefore, the level of expression of these channels in the interneurons under study is probably considerably dissimilar. The reason for incomplete suppression of the M current is perhaps the involvement of other potassium channels (e.g., those of Kv1 family) in the formation of this current. Neirofiziologiya/Neurophysiology, Vol. 38, No. 3, pp. 198–204, May–June, 2006.     

Two types of calcium-dependent channels of potassium outward current in the somatic membrane of Helix pomatia neurons

Characteristics of delayed potassium outward current were investigated during voltage clamp experiments on nonidentified intracellularly perfused neurons isolated from the snailHelix pomatia. A calcium-dependent potassium curent displaying special properties was shown to exist, apart from the voltage-operated potassium currents dependent on intracellular calcium ions . This type of current increases with a rise in the extracellular concentration of calcium ions , is not blocked by intracellular application of 10 mM EGTA and 77 mM fluoride, and may be suppressed by adding 1.5 mM cobalt ions to the extracellular fluid. This current, unlike , only takes a few milliseconds to peak, after which it fades to a steady level, comparable with that of .A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 19, No. 2, pp. 185–191, March–April, 1987.     

1-磷酸鞘氨醇对心肌细胞钾离子通道的作用

目的：研究1-磷酸鞘氨醇（S1P）对豚鼠心室肌细胞延迟整流钾电流（IK）、内向整流钾电流（IK1）的作用。方法：实验用胶原酶酶解法急性分离豚鼠心室肌细胞,利用全细胞膜片钳的方法记录心室肌细胞的延迟整流钾电流（IK）、内向整流钾电流（IK1）。结果：①应用S1P（1．1μmol／L）后IK从（1．24±0．26）nA降至（0．95±0．23）以（P〈0．01,n=6）,而S1P（2．2μmol／L）组IK从（1．43±0．31）nA下降到（1．02±0．28）nA,统计学有显著性差异（P〈0．01,H=6）.而S1P（1．1μmol／L）＋苏拉明（Summin）（200μmol／L）组与对照相比,IK峰值从（1．29±0．26）nA下降（1．26±0．37）nA,统计学无显著性差异（P〉0．05,n=6）．②应用S1P（1．1μmol／L,2．2μmol／L）后与对照组比较,S1P（1．1μmol／L,2．2μmol／L）分别使内向整流钾电流（IK1）峰值从（-8．94±2．01）nA和（-8．81±1．55）nA下降到（18．86±1．59）nA和（-8．55±1．39）nA,统计学无显著性差异（P〉0．05,n=6）.结论：S1P可降低豚鼠心室肌细胞延迟整流钾电流（IK）的幅值,同时S1P对豚鼠心室肌细胞内向整流钾通道（IK1）没有作用。     

Kv4.2通道电流与大鼠海马神经元瞬间外向钾电流特性的比较

本研究比较了转染的Kv4.2钾电流与原代培养大鼠海马神经元上瞬间外向钾电流(IA)动力学特征。实验采用瞬时转染,细胞培养和全细胞膜片钳记录等方法。结果表明:转染的Kv4.2通道电流和海马神经元上IA均具有明显的A型电流特征。海马神经元IA的半数最大激活电位和斜率因子分别为-10.0±3.3 mV和13.9±2.6 mV;半数最大失活电位和斜率因子分别为-93.0±11.4 mV和-9.0±1.5 mV;失活后再激活恢复时间常数(T)为27.9±14.1 ms。Kv4.2的半数最大激活电位和斜率因子分别为-9.7±4.1 mV和15.8±5.7 mV;半数最大失活电位和斜率因子分别为-59.4±12.2 mV和8.0±3.1 mV;Kv4.2的灭活后再激活的恢复时间常数τ为172.8±10.0 ms。结果提示:Kv4.2通道电流可能是海马神经元上的IA电流的主要成分,但不是唯一成分。     

Inhibition of the calcitonin-induced outward current in identifiedAplysia neurons by interleukin-1 and interleukin-2

Summary 1. The effects of bath-applied recombinant human interleukin-1 (rhIL-1) and interleukin-2 (rhIL-2) on the calcitonin (CT)-induced outward current recorded from identified neurons (R9–R12) ofAplysia kurodai were investigated with conventional voltage-clamp and pressure ejection techniques.2. Micropressure ejection of CT onto the soma of the neuron induced a slow outward current [I _o(CT); 4–6 nA in amplitude, 30–40 sec in duration] associated with a decrease in input membrane conductance.3.I _o(CT) was increased by hyperpolarization.4. The extrapolated reversal potential was +10 mV. Additionally,I _o(CT) was sensitive to changes in (Na⁺)_o but not to changes in (K⁺)_o, (Ca²⁺)_o, and (Cl^–)_o.5. Micropressure-ejected forskolin produced a slow outward current similar to that induced by CT.6. Bath-applied rhIL-1 and rhIL-2 (10–40 U/ml) reduced the CT-induced current in identifiedAplysia neurons without affecting the resting membrane conductance or the holding current.7. The inhibitory effects of both cytokines on the current were completely reversible. Heat-inactivated rhIL-1 and rhIL-2 were without effect.8. These results suggest that the immunomodulators, IL-1 and IL-2, can modulate the CT-induced outward current associated with a decrease in Na⁺ conductance in the nervous system ofAplysia. Therefore, the study suggests that these cytokines may also serve as neuromodulators.     

粒细胞巨噬细胞集落刺激因子诱导的巨噬细胞外向K+电流的特性

以粒细胞巨噬细胞集落刺激因子（ＧＭ－ＣＳＦ,１６ｎｇ／ｍｌ）长期（０．５－６ｄ）刺激小鼠腹腔渗了的巨噬细胞,采用全细胞膜片箝技术研究在ＧＭ－ＣＳＦ刺激过程中细胞膜电流的变化,观察到一种ＧＭ－ＣＳＦ诱导的瞬间失活的外向Ｋ电流,该电流在生理电压范围内可发生稳态失活,且当施加０．５ＨＺ的去极化脉冲刺激时其失活具有频率依赖性。该电流对胞外４－ＡＰ高度敏感,胞内Ｃａ＾２＋浓度「Ｃａ＾２＋」升主可抑制其幅度,     

兔心室肌细胞电生理异质性研究--缺血对动作电位和钾流的影响

实验用全细胞膜片箝技术,观察正常及缺血条件下,兔心内膜下心室肌细胞与心外膜下心室肌细胞的动作电位和稳态外向钾流及其变化。结果显示：（１）正常条件下,心外膜下心室肌细胞与心内膜下心室肌细胞动作电位形态有差异,心外膜下心室肌细胞动作电位时程（ＡＰＤ）较短,复极１期后有明显的初迹,动作电位形态是“锋和圆顶”,而心内膜下心室肌细胞ＡＰＤ较长,并且没有上述动作电位形态特征。这两类细胞静息电位无差异。（２）在     

间歇性低氧对大鼠心室肌细胞短暂外向电流的影响

利用全细胞膜片箝方法研究间歇性低氧后左、右心室肌细胞短暂外向电流（Ｉｔｏ）的变化,以探讨间歇性低氧增强心肌电稳定性的离子机制。大鼠间歇性暴露于低氧环境２８ｄ（Ｈ２８,６ｈ／ｄ）后,右心室肌细胞的Ｉｔｏ密度较常氧对照组明显增加（１６１８±４６１比６３２±１３５ｐＡ／ｐＦ,Ｐ＜００５）,而左心室肌细胞Ｉｔｏ密度与对照组无明显差异。间歇性低氧暴露４２ｄ（Ｈ４２）动物,其左、右心室肌细胞Ｉｔｏ密度与对照组无明显差异。Ｉｔｏ激活、失活和恢复动力学变化主要表现为Ｈ４２组左、右心室肌细胞的稳态失活曲线明显向负电压方向移位。左心室细胞的半数失活电压（－３８９±２３）ｍＶ与对照组（－３２８±５９）ｍＶ比较,具有显著性差异（Ｐ＜００１）;右心室细胞的半数失活电压（－４１９±４５）ｍＶ与对照组（－３３５±３５）ｍＶ比较,具有显著性差异（Ｐ＜０００１）。据此可推断,Ｉｔｏ密度的改变可反映心室在低氧早期阶段的不同动力学反应。失活动力学改变参与间歇性低氧心脏保护机制     

麻醉剂氟烷对心脏毒蕈碱型钾通道的影响

神经递质乙酰胆碱（ＡＣｈ）调节心脏功能最重要的离子通道就暗毒蕈碱型钾通道（ｉＫ,ＡＣｈ）,该通道由ＡＣｈ经鸟苷酸调节蛋白（Ｇ蛋白）的βγ亚单位而激活。本实验彩全细胞膜片箝方法,观察了麻醉药氟烷对豚鼠心房肌细胞ｉＫ,ＡＣｈ的影响。氟烷对ｉＫ,ＡＣｈ电流具抑制效应,灌注之后可使ＡＣｈ激活的ｉＫ,ＡＣｈ速率减慢,峰植下降。但其抑制ｉＫ,ＡＣｈ的程度依激活方式而异：经正常激活途径,即由ＡＣｈ激活毒蕈碱Ｍ样     

Evidence for a calcium-dependent outward conductance in endocrine cells of the cockroach, Diploptera punctata

Abstract The cell membranes of the corpora allata of the cockroach Diploptera punctata contain voltage-dependent calcium channels. Depolarizing current injection into cells of the corpora allata in the presence of the calcium channel blockers, cadmium, cobalt or verapamil allows the production of multiple action potentials, as does treatment with the intracellular calcium chelator, BAPTA/AM. These results suggest that calcium currents are involved both in decreasing the excitability and in activating an outward current in cells of the corpora allata. Electrophysiological measurements also suggest a concomitant reduction in outward conductance following the multiple action potentials produced in the presence of the channel blockers or BAPTA/ AM. We hypothesize that the calcium current may play an important role in the regulation of intracellular calcium concentration and Juvenile Hormone biosynthesis.     

Effects of carvedilol on transient outward and ultra-rapid delayed rectifier potassium currents in human atrial myocytes

Carvedilol is a beta- and alpha(1)-adrenoceptor antagonist. It is widely used in the treatment of cardiovascular diseases including atrial arrhythmias. However, it is unclear whether carvedilol may affect the repolarization currents, transient outward K(+) current (I(to)) and ultra-rapid delayed rectifier K(+) current (I(Kur)) in the human atrium. The present study evaluated effects of carvedilol on I(to) and I(Kur) in isolated human atrial myocytes by whole-cell patch-clamp recording technique. We found that carvedilol reversibly inhibited I(to) and I(Kur) in a concentration-dependent manner. Carvedilol (0.3 microM) suppressed I(to) from 9.2+/-0.5 pA/pF to 4.8+/-0.5 pA/pF (P<0.01) and I(Kur) from 3.6+/-0.5 pA/pF to 1.9+/-0.3 pA/pF (P<0.01) at +50 mV. I(to) was inhibited in a voltage-dependent manner, being significantly attenuated at test potentials from +10 to +50 mV, whereas the inhibition of I(Kur) was independent. The concentration giving a 50% inhibition was 0.50 microM for I(to) and 0.39 microM for I(Kur). Voltage-dependence of activation, inactivation and time-dependent recovery from inactivation of I(to) were not altered by carvedilol. However, time to peak and time-dependent inactivation of I(to) were significantly accelerated, indicating an open channel blocking action. The findings indicate that carvedilol significantly inhibits the major repolarization K(+) currents I(to) and I(Kur) in human atrial myocytes.     

Lipopolysaccharide induction of outward potassium current expression in human monocyte-derived macrophages: Lack of correlation with secretion

Summary Although an outwardly rectifying K⁺ conductance (I _K, A) is prominently expressed in human alveolar macrophages, the expression of this conductance in human monocyte-derived macrophages (HMDMs) is rare. We have analyzed the induction of the expression of I _K, A in voltage-clamped, in vitro differentiated HMDMs by a number of stimuli which produce either priming or activation of macrophages. Cultures were stimulated with lipopolysaccharide (LPS, 2 g/ml), interleukin 2 (IL-2, 100 U/ml), or combinations of LPS and either recombinant interferon-gamma (-IFN, 10 U/ml), phorbol myristate acetate (PMA, 0.01 or 1 g/ ml) and platelet activating factor (PAF, 20 ng/ml) for periods of up to 24 hr. Treatment of the cells with either LPS or IL-2 greatly enhanced the frequency of current expression. Treatment with either PMA or -IFN alone did not induce current expression; treatment of the cells with a combination of LPS and either PMA, -IFN, or PAF did not enhance current expression over that observed with LPS alone. The expression of the outwardly rectifying K⁺ current was observed in 36% (n=321) of the cells for cultures treated with LPS and 33% (n=55) of the cells for cultures treated with IL-2. The inactivating outward K⁺ current was absent in cells which were not treated with either LPS or IL-2. The kinetics of current activation and inactivation appeared identical to that previously described for the transient-inactivating outward current of the human alveolar macrophage. Cycloheximide (1 g/ml), an inhibitor of protein synthesis, completely suppressed LPS-induced current expression. No correlation was found between peak current amplitude and cell size in LPS-activated cells expressing the outwardly rectifying K⁺ current, indicating that current density was not held constant from cell to cell. The coupling of ion channel expression and secretion in individual HMDMs was studied using the reverse hemolytic plaque assay. Although an enhancement of K ⁺ current expression was observed following either LPS or IL-2 treatment, a quantitatively similar and uniform increase in the percentage of either IL-1 or lysozyme-secreting cells was not observed. The frequency of current expression in cells identified as secreting tumor necrosis factor- (TNF-), interleukin 1 (IL-1), or lysozyme was the same or decreased over that observed for nonsecreting cells. Thus, LPS treatment increases the number of K⁺ channels on HMDM membranes; however, K⁺ channel expression alone was not sufficient to give rise to enhanced secretion in LPS-activated macrophages. Enhanced K⁺ channel expression appears to be a part of the primary activation signal. K⁺-channel activation would hyperpolarize the membrane potential, potentially providing the driving force for calcium entry through voltage-independent pathways activated by the subsequent binding of soluble substances to membrane surface receptors, the secondary signal linked to secretion.This work was supported by NIH grant RO 1 GM36823.     

The dual effect of rubidium ions on potassium efflux in depolarized frog skeletal muscle

Summary The effects of external Rb⁺ on the efflux of⁴²K⁺ from whole frog sartorius muscles loaded with 305mm K⁺ and 120mm Cl^– were studied. K⁺ efflux is activated by [Rb⁺] _o less than about 40mm according to a sigmoid relation similar to that for activation by [K⁺] _o . At [Rb⁺]_o greater than 40mm, K⁺ efflux declines, although at [Rb⁺] _o =300mm it is still greater than at [Rb⁺] _o =0mm. For low concentrations, the increment in K⁺ efflux over that in K⁺- and Rb⁺-free solution, k, is described by the relation k=a[X⁺] _o ⁿ , for both K⁺ and Rb⁺. The value ofa is larger for Rb⁺ than for K⁺, while the values ofn are similar; the activation produced by a given [Rb⁺] _o is larger than that by an equal [K⁺] _o for concentrations less than about 40mm. Adding a small amount of Rb⁺ to a K⁺-containing solution has effects on K⁺ efflux which depend on [K⁺] _o . At low [K⁺] _o , adding Rb⁺ increases K⁺ efflux, the effect being greatest near [K⁺] _o =30mm and declining at higher [K⁺] _o ; at [K⁺] _o above 40mm, addition of Rb⁺ decreases K⁺ efflux. At [K⁺] _o above 75mm, where K⁺ efflux is largely activated, Rb⁺ reduces K⁺ efflux by a factorb, described by the relationb=1/(1+c[Rb⁺] _o ). Activation is discussed in terms of binding to at least two sites in the membrane, and the reduction in K⁺ efflux by Rb⁺ at high [K⁺] _o in terms of association with an additional inhibitory site.     

银杏苦内酯B对缺血豚鼠心室肌动作电位、L-型钙电流和延迟整流钾电流的作用

目的:研究银杏苦内酯B对正常和缺血心室肌细胞动作电位(action potential,AP),L-型钙电流(L-type calcium current,ICa-L)、延迟整流钾电流(Delayed Rectifier Currennt,IK)的影响.方法:用常规细胞内微电极方法记录豚鼠心室肌细胞动作电位,用全细胞膜片钳技术记录游离心室肌细胞离子流.结果:①在生理条件下,银杏苦内酯B可缩短心室肌细胞动作电位时程 (action potential duration,APD),但对AP其他参数无影响,银杏苦内酯B可增大IK,呈浓度依赖性,但对ICa-L无显著作用;②在缺血条件下,APD50、APD90明显缩短,RP、APA减小,Vmax减慢,而银杏苦内酯B则可延缓和减轻缺血所引起上述参数的变化;3.在缺血条件下,IK和ICa-L均受到抑制,但加入银杏苦内酯B后可逆转缺血所造成这两种离子流的减小.结论:银杏苦内酯B可对抗心肌缺血所引起的心肌电生理的变化,提示银杏苦内酯B可预防心律失常的发生.