CATION CHANNEL BLOCKED BY EXTRACELLULAR CA2+ IN THE APICAL MEMBRANE OF THE CHICK EMBRYONIC ECTODERM
CATION CHANNEL BLOCKED BY EXTRACELLULAR CA2+ IN THE APICAL MEMBRANE OF THE CHICK EMBRYONIC ECTODERM
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DOI：
10.1007/bf00374311
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发表时间：
1994-12-01
影响因子：
4.5
通讯作者：
KUCERA, P
中科院分区：
文献类型：
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作者：
LI, JQ;PRODHOM, B;KUCERA, P
在鸡胚(孵化20h，原肠胚期)，外胚层细胞的顶膜显示出高密度的非选择性阳离子通道，该通道被极低的细胞外钙离子浓度所阻断。在细胞贴附模式下，采用膜片钳技术在单通道水平上研究了该通道的特性。当移液管中钙离子浓度为1 mmol/L时，只有外向电流，在+120 mV时测得的通道电导为25.5ps。在没有钙离子的情况下，也观察到通过该通道的内向电流。在-50 mV下，以Na+为载流子测得的电导为49.5ps，K+为72.5ps，Cs+为49.1 ps，Li+为18.5ps。4例患者在+80 mV时测得的电导均在23ps左右。四种离子的反转电势相似(约25 mV)，表明该通道的选择性较差。在无Ca~(2+)和1 mmol/L的乙二胺四乙酸酯存在下，该通道的动力学特征为秒量级的猝发。在一次爆发期间，通道在一个开放和一个关闭的水平之间闪烁。开放时间在-30 mV~-80 mV之间不变，关闭时间随超极化而缩短。开放时间因离子(K+)的不同而不同
In the chick embryo (20 h incubation, gastrula stage), the apical membrane of the ectodermal cells shows a high density of a non-selective cation channel which is blocked by very low extracellular Ca2+ concentrations. Properties of this channel were studied at the single-channel level using the patch-clamp technique in the cell-attached mode.With 1 mmol/l Ca2+ in the pipette, only outward current was present and the channel conductance measured at +120 mV was 25.5 pS. In the absence of Ca2+, also inward current through the channel was observed. The conductances measured at -50 mV were 49.5 pS with Na+ as the charge carrier, 72.5 pS with K+, 49.1 pS with Cs+, and 18.5 pS with Li+. The conductance measured at +80 mV was around 23 pS in all four cases. The reversal potential was similar (around 25 mV) for all four ions, which indicates a poor selectivity of the channel. In the absence of Ca2+ and the presence of 1 mmol/l ethylenebis(oxonitrilo)tetraacetate (EGTA), the kinetics of the channel were characterized by bursts of the order of seconds. During a burst, the channel flickered between one open and one closed level. The open time was constant between -30 mV and -80 mV, while the closed time decreased with hyperpolarization. The open time varied according to the permeant ion (K+