The action of blocking agents applied to the inner face of Ca2+-activated K+ channels from human erythrocytes
The action of blocking agents applied to the inner face of Ca2+-activated K+ channels from human erythrocytes
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DOI：
10.1007/s002329900427
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发表时间：
1998-09-15
影响因子：
2.4
通讯作者：
Dunn, PM
中科院分区：
文献类型：
--
作者：
Dunn, PM
克霉唑和西替地尔，两种已知抑制Gardos通道的药物，已经研究了对来自人红细胞的由内而外的膜片中的单个中间电导钙激活钾（IK（Ca））通道的作用，并与TEA和Ba（2+）应用于膜的胞质面的作用进行了比较。TEA产生快速阻断，其被观察为单通道电流幅度的降低。这种效应是弱电压依赖性的，TEA在其结合位点（delta）处感测到的膜电位的分数为0.18，0 mV时的K（d）为20.5 mM。Ba（2+）是通道的非常有效的阻断剂，将单通道活动打破成爆发，散布有持续数秒的沉默期。Ba（2+）的作用对电压非常敏感，δ = 0.44，0 mV时的K（d）为0.15 μ M。克霉唑以小于或等于1 μ M的浓度施加到膜的内表面产生缓慢的阻断，导致由持续数秒的静止期分隔的通道活性的爆发。克霉唑的效果被模仿的季衍生物UCL 1559，在保持在通道的细胞质面的行动。高浓度的西替地尔（100 μ M）只产生一个弱的通道块。这种作用的动力学非常缓慢，爆发和爆发间的间隔持续几分钟。虽然西替地尔对Gardos通道的抑制不太可能涉及细胞内作用位点，但如果克霉唑能够穿透细胞膜，则其部分作用可能是由于与通道上的细胞内位点结合。
The actions of clotrimazole and cetiedil, two drugs known to inhibit the Gardos channel, have been studied on single intermediate conductance calcium-activated potassium (IK(Ca)) channels in inside out patches from human red blood cells, and compared with those of TEA and Ba(2+) applied to the cytoplasmic face of the membrane. TEA produced a fast block which was observed as a reduction in the amplitude of the single channel current. This effect was weakly voltage dependent with the fraction of the membrane potential sensed by TEA at its binding site (delta) of 0.18 and a K(d) at 0 mV of 20.5 mM. Ba(2+) was a very potent blocker of the channel, breaking the single channel activity up into bursts, interspersed with silent periods lasting several seconds. The effect of Ba(2+) was very voltage sensitive, delta = 0.44, and a K(d) at 0 mV of 0.15 mu M. Clotrimazole applied to the inner face of the membrane at a concentration less than or equal to 1 mu M produced a slow block resulting in bursts of channel activity separated by quiescent periods lasting many seconds. The effect of clotrimazole was mimicked by a quaternary derivative UCL 1559, in keeping with an action at the cytoplasmic face of the channel. A high concentration of cetiedil (100 mu M) produced only a weak block of the channel. The kinetics of this action were very slow, with burst and inter-burst intervals lasting several minutes. While inhibition of the Gardos channel by cetiedil is unlikely to involve an intracellular site of action, if clotrimazole is able to penetrate the membrane, part of its effect may result from binding to an intracellular site on the channel.