前列腺素E1对豚鼠心室肌细胞ATP敏感K+通道的影响

目的从离子通道水平,探讨前列腺素E1(PGE1)对ATP敏感K+(KATP)通道的作用.方法膜片钳制技术全细胞记录模式.结果PGE1可诱导KATP通道开放并呈浓度依赖关系.保持电位-40mV,指令电位+20mV,持续时间1s条件下,,10μmol·L1PGE1使外向K+电流由给药前的(2.27±0.34)nA增加到(5.46±0.34)nA(n=6,P＜0.01),增加了(3.18±0.23)nA.并且增加的钾电流可被KATP通道特异阻断剂Glibenclamide(10μmol·     

Electrophysiologic effects of TYB-3823, a new antiarrhythmic agent, on isolated guinea pig ventricular muscles

The effects of a newly synthesized antiarrhythmic agent, TYB-3823 on the transmembrane action potential were examined in isolated papillary muscles of guinea pig. TYB-3823 (3 x 10(-6)-3 x 10(-5)M) caused a dose-dependent decrease in the maximum upstroke velocity (Vmax) and a shortening of action potential duration (APD). In the presence of TYB-3823, trains of stimuli at rates greater than or equal to 0.2 Hz led to an exponential decline in Vmax. This use-dependent block was enhanced at higher stimulation frequency. The time constant for the recovery of Vmax from the use-dependent block was 12.6-13.4 s. The curves relating membrane potential and Vmax were shifted by TYB-3823 (3 x 10(-5)M) to the direction of more negative potentials (5.7 mV). In preparations treated with TYB-3823 (10(-5)-3 x 10(-5) M), the Vmax of test action potentials preceded by conditioning clamp pulses to 0 mV was progressively decreased by increasing the duration of a single clamp pulse or by increasing the number of multiple brief clamp pulses. These findings suggest that TYB-3823 has use- and voltage-dependent inhibitory action on the fast sodium channel by binding to the channel during its activated and inactivated states, and that the unbinding rate of the drug from the channel is very slow. Such characteristics of sodium channel block in combination with APD shortening effect would provide unique antiarrhythmic activities of this substance.     

Electrophysiological effects of KT-362, a new antiarrhythmic agent with vasodilating action, on isolated guinea pig ventricular muscle

The effects of KT-362, a newly synthesized vasodilating and antiarrhythmic agent, on transmembrane action potentials were examined in isolated papillary muscles of guinea pig. KT-362 (3 x 10(-6) to 3 x 10(-5) M) caused a dose-dependent decrease in the maximum upstroke velocity (Vmax) of the action potential without affecting the resting potential. In the presence of KT-362, trains of stimuli at rates greater than or equal to 0.2 Hz led to an exponential decline in Vmax. This use-dependent block was enhanced at higher stimulation frequency. The time constant for the recovery of Vmax from the use-dependent block was 2.8-2.9 s. The curves relating membrane potential and Vmax were shifted by KT-362 (10(-5) M) in the direction of more negative potentials (8.6 mV). In papillary muscles treated with KT-362 (10(-5) M), the Vmax of test action potential preceded by conditioning clamp pulses to 0 mV was progressively decreased with increasing number of pulses, while it was little affected by the duration of each clamp pulse within the range from 10 to 700 ms. These findings suggest that KT-362 has quinidine-like use-dependent inhibitory action on the fast sodium channel of cardiac muscles by the binding to the channel mainly during its activated state. At high concentrations (greater than or equal to 3 x 10(-5) M), KT-362 also suppressed the slow action potential in K+ depolarized papillary muscles.     

三七皂甙单体Rb1对心肌细胞膜钙离子通道的影响

Ｒ２８４．１；Ｒ３３１．３８；Ｒ９７２．２；Ｒ９７２．４摘要目的观察Ｒｂ１对豚鼠心肌细胞膜Ｌ－型电压依赖性钙通道的影响。方法采用标准全细胞膜片钳技术（ｗｈｏｌｅ－ｃｅｌｐａｔｃｈｃｌａｍｐｒｅｃｏｒｄｉｎｇｔｅｃｈｎｉｑｕｅ）。结果在保持电位－４０ｍＶ，细胞去激化至＋４０ｍＶ，刺激频率０．５Ｈｚ，时程１５０ｍｓ条件下，Ｒｂ１１０μｍｏｌＬ－１和３０μｍｏｌＬ－１分别使ＢａｙＫ８６４４和ｎｉｆｅｄｉｐｉｎｅ敏感的钙内向电流减少１６．２％±３．７％（Ｐ＜０．０５，ｎ＝５）和３８．３％±１０．４％（Ｐ＜０．０１，ｎ＝５），且在３～１０００μｍｏｌＬ－１范围内，其抑制作用呈浓度依赖关系。结论实验证明Ｒｂ１为一钙通道阻滞剂。     

Electrophysiological effects of a novel antiarrhythmic drug, EO-122, on guinea pig ventricular muscle and isolated myocytes

EO-122, a newly developed structural analog of lidocaine, has recently been shown to suppress ventricular arrhythmias in a few clinical studies in patients and in experimental animals. In the present study, we investigated the effects of EO-122 on the electrophysiological properties of guinea pig papillary muscle and ventricular myocytes by means of standard microelectrode and whole-cell recording techniques, respectively, At the concentration range of 10(-7)-10(-4) M (cycle length, 2000 ms), resting potential and action potential duration (APD90) were not altered by the drug. Action potential amplitude and APD50 were reduced (p less than 0.01) by 10(-4) M, and Vmax was reduced (p less than 0.01) by EO-122 greater than or equal to 10(-5) M. The effect of EO-122 on Vmax was use-dependent. At 10(-6) and 10(-5) M (cycle length, 2000 ms), the time constant for onset of block (tau on) was 37.0 +/- 13.2 and 26.0 +/- 3.4 s, respectively. The recovery kinetics from use-dependent block was not monoexponential, and the estimated "time constant" for recovery was 76.5 s. We examined the effects of EO-122, 10(-5) M, on the membrane currents in ventricular myocytes and found that the drug attenuated the slow inward current (Isi). EO-122 reduced peak Isi by 68.6 +/- 5.2% (p less than 0.005), whereas the outward current was unchanged. The present study demonstrates that EO-122 blocks both the fast inward (Na+) and the slow inward (Ca2+) channels, and these effects are probably responsible for the antiarrhythmic effects of the drug.     

Sematilide blocks the inward rectifier potassium channel in isolated guinea pig ventricular myocytes

• 1.1. In whole-cell patch recording, the relative potency of the blocking action of sematilide on I_K1 was found to be constant at each potential level of I_K1 activation. Under more acidic condition, the degree of block was decreased. These results strongly suggested that the neutral form of sematilide may penetrate the cardiac cell membrane via hydrophobic pathway.
• 2.2. In cell-attached patches, sematilide prolonged the interburst interval and reduced the opening probabilities of the I_K1 channel without affecting either the mean open time or the mean closed time within a burst.

     

抗心律失常药E-4031通过蛋白激酶C途径影响豚 鼠心室肌细胞Na+/Ca2+交换 (英文)

应用全细胞电压钳技术的斜坡脉冲程序 ,测定离体豚鼠心肌细胞准稳态电流 -电压关系曲线 ,研究E- 40 31增强 Na /Ca2 交换电流的机理 .结果表明蛋白激酶 C激动剂十四酰佛波乙酯 ( TPA) 5,1 0和1 5nmol· L-1使膜电位 50 m V时的 Ni2 敏感电流分别增加 ( 1 1 6± 43) % ,( 2 2 5± 63) %和 ( 2 89±69) % .使膜电位 - 1 0 0 m V时的 Ni2 敏感电流分别增加 ( 2 9± 1 7) % ,( 1 0 4± 2 1 ) %和 ( 1 40± 2 9) % .蛋白激酶 C拮抗剂他莫昔芬 2 0 μmol· L-1可完全阻断 E- 40 31和 TPA对该电流的刺激作用 .结果提示 ,E- 40 31通过蛋白激酶 C途径激动 Na /Ca2 交换 .     

Electrophysiologic effects of nicainoprol, a putative class I antiarrhythmic agent, on the guinea pig ventricular papillary muscle

We examined the effects of nicainoprol (1-50 microM), a new antiarrhythmic agent, on the transmembrane action potentials in isolated papillary muscles of the guinea pig. Nicainoprol (greater than or equal to 5 microM) produced dose-dependent decreases in the maximal upstroke velocity (Vmax) of the action potential. Only the highest concentration (50 microM) decreased the amplitude and the overshoot of the action potential and shortened its duration at 50 or 90% repolarization levels (APD50, APD90). The potential at rest was not affected by any concentration tested (1-50 microM). In the presence of nicainoprol, trains of stimuli at the rate of 0.2, 0.5, 1.0, and 2.0 Hz, introduced after a sufficient period of rest, led to an exponential decay of the Vmax to the steady state levels (use-dependent block, UDB). The UDB was augmented with an increase in the stimulation frequency or with a decrease in the potentials at rest. The time constant for the recovery from the UDB was 51.6 +/- 9.4 s at 50 microM. The Vmax and the amplitude of the slow response elicited in the presence of 27 mM [K+]o and 0.2 mM Ba2+ was significantly decreased by application of nicainoprol (10-100 microM), with a significant shortening of APD50 (100 microM). These findings suggest that nicainoprol has electrophysiologic properties in common with those of other class I antiarrhythmic drugs with slow kinetics (Ic) and has a minor but significant inhibitory effect on slow inward current (class IV effect).     

Effect of SUN 1165, a new potent antiarrhythmic agent, on the kinetics of rate-dependent block of Na channels and ventricular conduction of extrasystoles

Effects of SUN 1165, disopyramide, lorcainide, and mexiletine were studied either on the kinetics of onset of and recovery from rate-dependent depression of maximum rate of rise of phase 0 action potential (Vmax) in isolated guinea pig papillary muscles using standard microelectrode techniques or on intraventricular conduction time of extrasystoles evoked at varied coupling intervals in anesthetized dogs. SUN 1165 and lorcainide produced a slow-developing rate-dependent block of Vmax with the rate constant of 0.12 AP-1 and 0.09 AP-1, respectively. Mexiletine also produced a rate-dependent block of Vmax, but with very rapid onset so as not to be fitted by a single exponential curve. Disopyramide produced an intermediate rate-dependent block of Vmax with the rate constant of 0.46 AP-1. The time constants for recovery from the rate-dependent block for SUN 1165, lorcainide and disopyramide were 27.3-28.2, 23.2, and 17.0 s, respectively, while that for mexiletine was 0.118 s. SUN 1165, lorcainide, and disopyramide slowed ventricular conduction time of extrasystoles at all coupling intervals of 800-250 ms. On the other hand, mexiletine slowed conduction time at short coupling intervals of 500-250 ms. These findings suggest that, like lorcainide, SUN 1165 belongs to class Ic antiarrhythmic agents, and that SUN 1165 and lorcainide as well as disopyramide with slow and intermediate kinetics and mexiletine with fast kinetics may inhibit ventricular extrasystoles conducted at long and short range of coupling intervals, respectively.     

前列腺素E1对豚鼠心室肌细胞ATP敏感K^＋通道的影响

目的　从离子通道水平 ,探讨前列腺素E1(PGE1)对ATP敏感K (KATP)通道的作用。方法　膜片钳制技术全细胞记录模式。结果　PGE1可诱导KATP通道开放并呈浓度依赖关系。保持电位 - 40mV ,指令电位 2 0mV ,持续时间 1s条件下 ,10 μmol·L-1PGE1使外向K 电流由给药前的 (2 2 7± 0 34 )nA增加到 (5 46± 0 34 )nA(n =6 ,P <0 0 1) ,增加了 (3 18± 0 2 3)nA。并且增加的钾电流可被KATP通道特异阻断剂Glibenclamide(10 μmol·L-1)抑制 ,抑制率是 6 3%± 7% (n =5 ,P <0 0 1)。结论　PGE1可开放豚鼠心室肌细胞KATP通道     

Electrophysiological properties of HBI-3000: a new antiarrhythmic agent with multiple-channel blocking properties in human ventricular myocytes

HBI-3000 (sulcardine sulfate) has been shown to suppress various ventricular arrhythmias in animal models. The electrophysiological properties of HBI-3000 were investigated using standard microelectrode and patch-clamp techniques in single human ventricular myocytes. HBI-3000 led to concentration-dependent suppression of dofetilide-induced early afterdepolarizations in single nonfailing human ventricular myocytes and early afterdepolarizations seen in failing ventricular myocytes. The concentration-dependent prolongation of action potential duration (APD) by HBI-3000 was bell shaped with maximum response occurring around 10 μM. Interestingly, HBI-3000 at the concentration of 10 μM modestly prolonged the APD at all 3 basic cycle lengths. The slope of APD-cycle length curve of HBI-3000 was only slightly steeper than that of control (88.8 ± 7.7 ms/s vs. 78.9 ± 5.2 ms/s in control, n = 8, P > 0.05). HBI-3000 only showed a minimal use-dependent prolongation of the APD in human ventricular myocytes. HBI-3000 inhibited fast sodium current (INa-F), late sodium channel (INa-L), L-type calcium current (ICa-L), and rapidly activating delayed rectifier K current (IKr) in single human ventricular myocytes. The estimated half-maximal inhibitory concentration values of INa-F, INa-L, ICa-L, and IKr were 48.3 ± 3.8, 16.5 ± 1.4, 32.2 ± 2.9, and 22.7 ± 2.5 μM, respectively. The ion channel profile and electrophysiological properties of HBI-3000 are similar to those of ranolazine and chronic amiodarone (reduced INa-F, INa-L, ICa-L, and IKr). HBI-3000 may be a promising antiarrhythmic agent with low proarrhythmic risk.     

Effect of antiarrhythmic drug E 4031 on Na /Ca 2 exchange currents in isolated guinea pig ventricular myocytes

应用全细胞电压钳的斜坡脉冲程序测定离体豚鼠心肌细胞准稳态电流电压关系曲线,研究Ⅲ类抗心律失常药Ｅ－４０３１对Ｎａ＋／Ｃａ２＋交换电流的影响,结果表明Ｅ－４０３１０．１,１．０,１０,５０μｍｏｌ·Ｌ－１使Ｎｉ２＋敏感电流浓度依赖性增加,膜电位＋５０ｍＶ时分别增加（７０±３８）％,（９１±５３）％,（１１８±６３）％,（１２２±５１）％;膜电位－１００ｍＶ时增加（２５±２０）％,（５１±３２）％,（１１３±８４）％,（９３±７３）％。提示Ｅ－４０３１对心室肌细胞Ｎａ＋／Ｃａ２＋交换电流的增强作用可能是其正性变力作用的重要机理。     

Increase of the ventricular fibrillation threshold by 711389-S, a new antiarrhythmic agent, in guinea-pigs

The increase of the ventricular fibrillation threshold (VFT) by 711389-S, a new antiarrhythmic agent, was compared with several other antiarrhythmic drugs using both in vitro (Langendorff) and in vivo preparations of guinea-pigs. The doses of antiarrhythmic drugs for increasing VFT by 10 volts in in vitro (microgram) and in vivo (mg/kg, i.v.) preparations were as follows: 711389-S: 4.2, 0.15; disopyramide: 32.6, 0.86; quinidine: 32.0, 0.57; aprindine: 7.6, 0.55; propranolol: 16.6, 0.57; and lidocaine: 20.7, 1.52. The duration of the antifibrillatory effects of 711389-S almost corresponded with those of aprindine and propranolol.     

Effects of S-1389 (711389-S), a new antiarrhythmic agent, on the conduction in perfused guinea pig hearts

In the His bundle and ventricular electrograms of Langendorff-perfused guinea pig hearts driven at a cycle length of 450 or 700 msec, S-1389 (711389-S), a new antiarrhythmic agent, above 3 x 10(-7) or 10(-6) M increased the basal conduction times in the following order: His-Purkinje system greater than ventricular and atrial muscles greater than atrioventricular (AV) node. Slowing of the ventricular and AV nodal conduction of extrasystoles with variable coupling intervals was also caused by S-1389. S-1389 above 10(-6) or 3 x 10(-6) M significantly prolonged the functional and/or effective refractory periods of the AV node and ventricle. Disopyramide (3 x 10(-6)-3 x 10(-5) M) also produced similar effects, but they were much less potent than those of S-1389. Although disopyramide did not produce the rate-dependent increases in the atrial and AV nodal conduction times and in the AV nodal refractory period, S-1389 increased these parameters rate-dependently.     

苦参碱对豚鼠心肌细胞钾电流的抑制作用(英文)

目的研究苦参碱对豚鼠心肌细胞动作电位时程和钾电流的影响,探讨其抗心律失常作用的可能机制。方法应用全细胞膜片钳技术记录心室肌细胞的动作电位时程和钾电流。结果在频率0.1Hz时,苦参碱100μmol.L-1以非频率依赖方式延长动作电位复极90%的时程达40%,在-120mV抑制内向整流钾电流(IK1)接近47%,减少快激活延迟整流钾电流的尾电流达50%,对慢激活延迟整流钾电流的尾电流无影响。结论苦参碱抗心律失常的机制可能与其抑制多种钾电流和延长动作电位时程有关。     

New positive inotropic agent OPC-8212 modulates single Ca2+ channels in ventricular myocytes of guinea pig

The effects of a new positive inotropic drug, OPC-8212 (a quinolinone derivative, 3,4-dihydro-6-[4-(3,4-dimethoxybenzoyl)-1 -piperazinyl]-2(1H)-quinolinone), on whole-cell and single-channel calcium currents of guinea pig ventricular myocytes were studied by the patch-clamp method. OPC-8212 increased whole-cell calcium currents in a concentration-dependent manner. The concentration-response curve was fitted by a single binding site model that has an ED50 of 2.7 microM. At the single-channel level, OPC-8212 increased calcium currents mainly by increasing the probability of channel opening on depolarization; the open times were slightly increased, but single-channel conductance did not change. The actions of OPC-8212 on single calcium channel currents were compared with those of forskolin, isoproterenol, and caffeine, agents that cause positive inotropic effects associated with an increase in cytoplasmic cyclic AMP level, and with those of the dihydropyridine calcium channel agonist (-)Bay K 8644, an agent that has a positive inotropic effect but does not act through cyclic AMP. OPC-8212 increased calcium currents in a manner that resembled the actions of forskolin, isoproterenol, and caffeine rather than the actions of (-)Bay K 8644. We suggest that activation of calcium currents by OPC-8212 is mediated by an elevation of intracellular cyclic AMP. Since OPC-8212 produces bradycardia and antitachycardiac effects in animals and humans, unlike agents that increase cyclic AMP, additional effects on other currents are likely.     

抗心律失常药E-4031通过蛋白激酶C途径影响豚鼠心室肌细胞Na+/Ca2+交换

应用全细胞电压钳技术的斜坡脉冲程序,测定离体豚鼠心肌细胞准稳态电流-电压关系曲线,研究E-4031增强Na⁺/Ca²⁺交换电流的机理. 结果表明蛋白激酶C激动剂十四酰佛波乙酯（TPA）5,10和15 nmol·L^-1使膜电位+50 mV时的Ni²⁺敏感电流分别增加（116±43）%,（225±63）% 和（289±69）%. 使膜电位-100 mV时的Ni²⁺敏感电流分别增加（29±17）%,（104±21）%和（140±29）%. 蛋白激酶C拮抗剂他莫昔芬20 μmol·L^-1可完全阻断E- 4031和TPA对该电流的刺激作用. 结果提示,E-4031通过蛋白激酶C途径激动Na⁺/Ca²⁺交换.     

Electrophysiological effects of OPC-88117, a new antiarrhythmic agent on papillary muscles and single ventricular myocytes isolated from guinea-pig hearts.

1. The effects of OPC-88117, a new antiarrhythmic agent, on transmembrane action potentials were examined in right ventricular papillary muscles and in single ventricular myocytes isolated from guinea-pig hearts. 2. In papillary muscles, OPC-88117 above 3 x 10(-6) M caused a dose-dependent prolongation of action potential duration (APD). 3. OPC-88117 above 3 x 10(-5) M caused a significant decrease in the maximum upstroke velocity (Vmax) of the action potential without affecting the resting membrane potential. The inhibition of Vmax was enhanced at higher stimulation frequencies. 4. In the presence of OPC-88117, trains of stimuli at rates greater than or equal to 1.0 Hz led to a use-dependent inhibition of Vmax with rapid onset. The time constant for the recovery of Vmax from the use-dependent block was 456 ms. 5. The curves relating membrane potential and Vmax were shifted by OPC-88117 to the direction of more negative potentials (9 mV at 10(-4) M). 6. In single ventricular myocytes treated with OPC-88117 (1-3 x 10(-4) M), the Vmax of test action potentials preceded by conditioning clamp pulses to 0 mV was decreased progressively as the clamp pulse duration was prolonged. 7. These findings suggest that the primary electrophysiological effect of OPC-88117 on the cardiac muscle cell is prolongation of APD (Class III action) and that at high concentrations, it may also possess a lignocaine-like sodium channel inhibitory effect (Class I action).     

Modulation of the delayed K+ current by histamine in guinea pig ventricular myocytes

Summary The effects of histamine on delayed K⁺ current (I_K) were investigated in patch-clamped single guinea pig ventricular myocytes. Histamine increased I_K with a maximal fractional response of 2.7 and a k_d of 9.4 × 10^–7 mol/l. At a concentration of 10^–8 mol/l, histamine did not increase I_K significantly, but increased I_Ca by 52% ± 12%. The voltage-dependence of I_K activation, the reversal potential and the time course of the I_K tail decay were not changed by histamine. Under pretreatment with 10^–4 mol/l of ranitidine, neither histamine (10^–6 mol/l) nor 2-pyridylethylamine (10^–4 mol/l) caused any sizable increase in I_K. When the cell was pretreated with a saturating dose of isoproterenol (10^–6 mol/l), histamine did not additively enhance I_K. The I_K enhancement by 3 × 10^–7 mol/l histamine was partially antagonized by concurrent exposure to 5 × 10^–6 mol/l carbachol. Whereas, use of a higher concentration of histamine (10^–6 mol/l) obscured the inhibitory effect of carbachol. It is concluded that histaminergic action of I_K is attributed exclusively to H₂ receptor-mediated reactions involving G_s protein and adenylate cyclase. Send offprint requests to Y. Habuchi at the above address