BLOCKAGE OF SQUID AXON POTASSIUM CONDUCTANCE BY INTERNAL TETRA-N-ALKYLAMMONIUM IONS OF VARIOUS SIZES
BLOCKAGE OF SQUID AXON POTASSIUM CONDUCTANCE BY INTERNAL TETRA-N-ALKYLAMMONIUM IONS OF VARIOUS SIZES
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DOI：
10.1016/s0006-3495(81)84849-7
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发表时间：
1981-01-01
影响因子：
3.4
通讯作者：
SHOUKIMAS, JJ
中科院分区：
文献类型：
--
作者：
FRENCH, RJ;SHOUKIMAS, JJ
本文研究了四烷基铵离子（CnH_（2n +1））~ 4 N ~+（n = 1-6）对电压钳制鱿鱼巨轴突K电导的影响。使用四己基铵的研究未进行定性分析，因为其影响不充分可逆。当添加到内部灌注液中时，这一系列大小分级的对称离子中的每一个都阻断K电导。存在阻断效力随尺寸增加而增加的一般趋势。这归因于较长的烷基侧链与通道附近的膜的疏水区域的较强的相互作用。TAA离子的稳态阻断，n = 2-5，显示出相同的电压依赖性，明显地感测约15%的跨膜电压，并且阻断开始的动力学在定性上相似。这些离子的作用部位是相同的。TMA [四甲基铵]的阻断作用对电压的依赖性大约是其两倍。在其作用中，TMA更类似于碱金属阳离子，而不是更大的TAA离子。进入K通道的内口可能比以前想象的要少。计算表明，通道的内腔不能既宽到足以接纳TAA离子，又长到足以解释阻断的电压依赖性。解决这一问题的可能途径被认为是。
The effects of the tetra-n-alkylammonium (TAA) ions, (CnH2n+1)4N+, n = 1-6, on the K conductance of voltage-clamped squid giant axons were studied. Studies using tetrahexylammonium were not qualitatively analyzed as its effect was insufficiently reversible. Each in this series of symmetric ions of graded size blocks the K conductance when added to the internal perfusion fluid. There is a general trend for blocking potency to increase with increasing size. This is attributed to stronger interactions of the longer alkyl side chains with hydrophobic regions of the membrane near the channels. Steady-state block by the TAA ions, n = 2-5, showed identical voltage dependence, apparently sensing about 15% of the transmembrane voltage, and kinetics of block onset were qualitatively similar. The site of action for these ions is the same. Block by TMA [tetramethylammonium] is about twice as steeply dependent on voltage. In its action, TMA resembles the alkali cations more than the larger TAA ions. Access to the inner mouth of the K channel probably is less restricted than previously thought. A calculation indicates that the lumen of the channel cannot be both wide enough to admit the TAA ions and long enough to account for the voltage dependence of block. Possible ways of resolving this praradox are considered.