Block of wild-type and inactivation-deficient cardiac sodium channels IFM/QQQ stably expressed in mammalian cells

被引:46
作者
Grant, AO
Chandra, R
Keller, C
Carboni, M
Starmer, CF
机构
[1] Duke Univ, Dept Med, Durham, NC 27706 USA
[2] Duke Univ, Dept Pediat, Durham, NC 27706 USA
[3] Med Univ S Carolina, Dept Biometry, Charleston, SC 29426 USA
关键词
D O I
10.1016/S0006-3495(00)76538-6
中图分类号
Q6 [生物物理学];
学科分类号
071011 ;
摘要
The role of inactivation as a central mechanism in blockade of the cardiac Na+ channel by antiarrhythmic drugs remains uncertain. We have used whole-cell and single channel recordings to examine the block of wild-type and inactivation-deficient mutant cardiac Na+ channels, IFM/QQQ, stably expressed in HEK-293 cells. We studied the open-channel blockers disopyramide and flecainide, and the lidocaine derivative RAD-243. All three drugs blocked the wild-type Na+ channel in a use-dependent manner. There was no use-dependent block of IFM/QQQ mutant channels with trains of 20 40-ms pulses at 150-ms interpulse intervals during disopyramide exposure. Flecainide and RAD-243 retained their use-dependent blocking action and accelerated macroscopic current relaxation. All three drugs reduced the mean open time of single channels and increased the probability of their failure to open. From the abbreviation of the mean open times, we estimated association rates of similar to 10(6)/M/s for the three drugs. Reducing the burst duration contributed to the acceleration of macroscopic current relaxation during exposure to flecainide and RAD-243. The qualitative differences in use-dependent block appear to be the result of differences in drug dissociation rate. The inactivation gate may play a trapping role during exposure to some sodium channel blocking drugs.
引用
收藏
页码:3019 / 3035
页数:17
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