The Membrane Potential of Nitella translucens
The Membrane Potential of Nitella translucens
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半透明 Nitella 的膜潜力
DOI：
10.1093/jxb/18.1.1
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发表时间：
1967
影响因子：
6.9
通讯作者：
E. Williams
中科院分区：
文献类型：
--
作者：
R. M. Spanswick;J. Stolark;E. Williams
本文研究了改变外界Na、K、Ca和Cl浓度对丽藻（Nitellaeroducens）节间细胞胞质和液泡相对于浸浴介质电位的影响。液泡和细胞质之间的电位差实际上不受浓度变化的影响。因此，观察到的电位差变化归因于将细胞质与培养基分离的边界;该边界可能是质膜-细胞壁复合物。细胞壁和介质之间的电位差也已被测量，并在钙的存在下，显示出显着敏感的外部钙浓度。结果分为两部分：（a）对于在5 mM NaCl中预处理的细胞，随后的实验在无Ca培养基中进行，和（B）对于最初浸入含有Na、K和Ca的氯化物的标准人工池水中的细胞。结果表明，在一定浓度范围内，细胞质-介质电位差可用一个与Goldman方程类似的方程来描述，但只包含Na和K项，渗透率比α（= PNa/PK）的平均值为0.27。在Ca存在下，Na和K对细胞质-介质电位差的影响大大降低，而Ca的影响相对较大。结果不能拟合到包含主要离子项的任何形式的戈德曼方程。简要讨论了生电泵对质膜电位的贡献的可能性。对预处理后的细胞进行了细胞质和液泡中Na、K含量的测定。细胞质中的Na浓度为37 mM，液泡中的Na浓度为73 mM;细胞质中的K浓度为93 mM，液泡中的K浓度为67 mM。两种离子的能斯特电位与细胞质介质和细胞质液泡电位差进行了比较。这种分析表明，钠是积极从细胞质运输到介质中，以及进入液泡; K被泵入细胞质从介质中，但似乎是接近整个液泡膜的电化学平衡。这证实了以前发表的工作。
The effects of changing the external concentrations of Na, K, Ca, and Cl on the potentials of the cytoplasm and the vacuole with respect to the bathing medium of the internodal cells of Nitella translucens have been investigated. The potential difference between the vacuole and the cytoplasm is practically unaffected by the concentration changes. The observed changes of potential difference are therefore attributed to the boundary separating the cytoplasm from the medium; this boundary is possibly a plasmalemma—cell wall complex. The difference of potential between the cell wall and the medium has also been measured and, in the presence of Ca, shown to be markedly sensitive only to the external Ca concentration. The results are divided into two sections: (a) for cells pretreated in 5 mM NaCl, the subsequent experiments being carried out in Ca-free media, and (b) for cells initially immersed in a standard artificial pond water containing the chlorides of Na, K, and Ca. With the pretreated cells the external Na/K ratio was varied with the total NaCl + KCl concentration kept constant at 1.1 mM. The results suggest that over a limited range of concentrations the cytoplasm-medium potential difference can be described by an equation similar in form to a Goldman equation but containing only terms for Na and K, the average value of the permeability ratio α (= PNa/PK) being 0.27. In the presence of Ca the effects of Na and K on the cytoplasm-medium potential difference are greatly reduced, while the effect of Ca is relatively large. The results cannot be fitted to any form of Goldman equation containing terms for the major ions. The possibility of a contribution to the plasmalemma potential from electrogenic pumps is briefly discussed. Measurements of the Na and K content of the cytoplasm and the vacuole have been made for the pretreated cells. The Na concentration in the cytoplasm is 37 mM and in the vacuole 73 mM; the K concentration is 93 mM in the cytoplasm and 67 mM in the vacuole. The Nernst potentials for both ions are compared with the cytoplasm-medium and cytoplasm-vacuole potential differences. This analysis shows that Na is actively transported from the cytoplasm into the medium as well as into the vacuole; K is pumped into the cytoplasm from the medium but appears to be close to electrochemical equilibrium across the tonoplast. This confirms previously published work.