Sodium conductance and the activation potential inXenopus laevis eggs
Sodium conductance and the activation potential inXenopus laevis eggs
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非洲爪蟾卵的钠电导和激活电位
DOI：
10.1007/bf00591094
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发表时间：
1985
期刊：
影响因子：
--
通讯作者：
E. Mancinelli
中科院分区：
文献类型：
--
作者：
A. Peres;E. Mancinelli
已经进行了实验以确定引起非洲爪蛙卵激活电位的膜通透性变化。这些卵子被人工激活，要么通过刺痛，要么通过在浴缸中添加钙离子载体A23187来激活。两种不同的离子电流似乎控制着激活电位：(I)氯电流，从激活刺激延迟30 S到5min后产生，在低氯时产生去极化；(Ii)电压依赖的外向电流，当膜电位大于约+20 mV时开始流动，并倾向于超极化。氯电流持续约3-4分钟；电压相关的外向电流在激活前就存在，并且比氯−电流消失得更慢。外源钠离子浓度的变化影响内向Cl-−电流形成前后外向电流的反转电位。我们认为，氯电流具有产生阻断多精细胞所需的快速去极化的作用，而电压依赖的钠外向电流可能阻止去极化达到过高的值，并有助于复极化阶段。
Experiments have been performed to identify the membrane permeability changes causing activation potential inXenopuseggs. The eggs were artificially activated either by pricking or by addition of the Ca2+ionophore A23187 to the bath. Two different ionic currents appear to control the activation potential: (i) a chloride current which develops after a delay of 30 s to 5 min from the activating stimulus and which, in low external chloride, produces a depolarization and, (ii) a voltage-dependent outward current which begins to flow when the membrane potential is more positive than about +20 mV and tends to hyperpolarize the membrane. The chloride current lasts about 3–4 min; the voltage-dependent outward current is present before activation and disappears more slowly than the Cl−current. Changes in external sodium concentration affect the reversal potential of the outward current before and after the development of the inward Cl−current. We suggest that the chloride current has the role of producing a rapid depolarization necessary to block polyspermy, while the voltage-dependent sodium outward current might prevent the depolarization from reaching excessively high values and help the repolarization phase.