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Comparison of the effects of antiarrhythmic drugs flecainide and verapamil on fKv1.4?N channel currents in Xenopus oocytes.

ABSTRACT: AIM: To study the effects of Na(+) channel blocker flecainide and L-type Ca(2+) channel antagonist verapamil on the voltage-gated fKv1.4?N channel, an N-terminal-deleted mutant of the ferret Kv1.4 K(+) channel. METHODS: fKv1.4?N channels were stably expressed in Xenopus oocytes. The K(+) currents were recorded using a two-electrode voltage-clamp technique. The drugs were administered through superfusion. RESULTS: fKv1.4?N currents displayed slow inactivation, with a half-inactivation potential of -41.74 mV and a slow recovery from inactivation (?=1.90 s at -90 mV). Flecainide and verapamil blocked the currents with IC(50) values of 512.29 ± 56.92 and 260.71 ± 18.50 ?mol/L, respectively. The blocking action of the drugs showed opposite voltage-dependence: it was enhanced with depolarization for flecainide, and was attenuated with depolarization for verapamil. Both the drugs exerted state-dependent blockade on fKv1.4?N currents, but verapamil showed a stronger use-dependent blockage compared with flecainide. Flecainide accelerated the C-type inactivation rate without affecting the recovery kinetics and the steady-state activation. Verapamil also accelerated the inactivation kinetics of the currents, but unlike flecainide, it affected both the recovery and the steady-state activation, causing slower recovery of fKv1.4?N channel and a depolarizing shift of the steady-state activation curve. CONCLUSION: The results demonstrate that widely used antiarrhythmic drugs flecainide and verapamil substantially inhibit fKv1.4?N channels expressed in Xenopus oocytes by binding to the open state of the channels. Therefore, caution should be taken when these drugs are administered in combination with K(+) channel blockers to treat arrhythmia.

SUBMITTER: Chen H

PROVIDER: S-EPMC4011620 | biostudies-literature | 2013 Feb

REPOSITORIES: biostudies-literature

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Comparison of the effects of antiarrhythmic drugs flecainide and verapamil on fKv1.4ΔN channel currents in Xenopus oocytes.

Chen Hui H Zhang Dong D Chao Sheng-ping SP Ren Jiang-hua JH Xu Lin L Jiang Xue-jun XJ Wang Shi-min SM

Acta pharmacologica Sinica 20121203 2

<h4>Aim</h4>To study the effects of Na(+) channel blocker flecainide and L-type Ca(2+) channel antagonist verapamil on the voltage-gated fKv1.4ΔN channel, an N-terminal-deleted mutant of the ferret Kv1.4 K(+) channel.<h4>Methods</h4>fKv1.4ΔN channels were stably expressed in Xenopus oocytes. The K(+) currents were recorded using a two-electrode voltage-clamp technique. The drugs were administered through superfusion.<h4>Results</h4>fKv1.4ΔN currents displayed slow inactivation, with a half-inact ...[more]

PMID: 23202797

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Project description:BACKGROUND:A new type of influenza virus, known as type D, has recently been identified in cattle and pigs. Influenza D virus infection in cattle is typically asymptomatic; however, its infection in swine can result in clinical disease. Swine can also be infected with all other types of influenza viruses, namely A, B, and C. Consequently, swine can serve as a "mixing vessel" for highly pathogenic influenza viruses, including those with zoonotic potential. Currently, the only antiviral drug available targets influenza M2 protein ion channel is not completely effective. Thus, it is necessary to develop an M2 ion channel blocker capable of suppressing the induction of resistance to the genetic shift. To provide a basis for developing novel ion channel-blocking compounds, we investigated the properties of influenza D virus M2 protein (DM2) as a drug target. RESULTS:To test the ion channel activity of DM2, the DNA corresponding to DM2 with cMyc-tag conjugated to its carboxyl end was cloned into the shuttle vector pNCB1. The mRNA of the DM2-cMyc gene was synthesized and injected into Xenopus oocytes. The translation products of DM2-cMyc mRNA were confirmed by immunofluorescence and mass spectrometry analyses. The DM2-cMyc mRNA-injected oocytes were subjected to the two-electrode voltage-clamp (TEVC) method, and the induced inward current was observed. The midpoint (Vmid) values in Boltzmann modeling for oocytes injected with DM2-cMyc RNA or a buffer were -152 and -200 mV, respectively. Assuming the same expression level in the Xenopus oocytes, DM2 without tag and influenza C virus M2 protein (CM2) were subjected to the TEVC method. DM2 exhibited ion channel activity under the condition that CM2 ion channel activity was reproduced. The gating voltages represented by Vmid for CM2 and DM2 were -141 and -146 mV, respectively. The reversal potentials observed in ND96 for CM2 and DM2 were -21 and -22 mV, respectively. Compared with intact DM2, DM2 variants with mutation in the YxxxK motif, namely Y72A and K76A DM2, showed lower Vmid values while showing no change in reversal potential. CONCLUSION:The M2 protein from newly isolated influenza D virus showed ion channel activity similar to that of CM2. The gating voltage was shown to be affected by the YxxxK motif and by the hydrophobicity and bulkiness of the carboxyl end of the molecule.

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Dataset Information

Comparison of the effects of antiarrhythmic drugs flecainide and verapamil on fKv1.4?N channel currents in Xenopus oocytes.

Publications

Comparison of the effects of antiarrhythmic drugs flecainide and verapamil on fKv1.4ΔN channel currents in Xenopus oocytes.

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