Ion transport in Nitellopsis obtusa.
Ion transport in Nitellopsis obtusa.
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DOI：
10.1085/jgp.42.2.335
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发表时间：
1958-11-20
期刊：
影响因子：
--
通讯作者：
DAINTY J
中科院分区：
文献类型：
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作者：
MACROBBIE EA;DAINTY J
研究了皮质轮虫 Nitellopsis obtusa 的单个节间细胞中钠、钾和氯离子的分布和交换速率。在示踪剂实验中，发现了三个动力学隔室，即细胞最外层的“自由空间”，我们称之为“原生质非自由空间”的隔室，以及细胞液。液泡中的浓度为 54 mM Na+、113 mM K+ 和 206 mM Cl-。穿过液泡膜的稳态通量为0.4 pmole Na+/cm.2 秒、0.25 pmole K+/cm.2 秒和0.5 pmole Cl-/cm.2 秒。原生质Na/K比与液泡中的相等，但原生质氯相对低得多。渗透考虑建议层厚为 4 至 6 µ，钠和钾浓度接近液泡中的浓度。原生质和外部溶液之间的通量约为8皮摩尔Na+/cm.2秒。和 4 pmole K+/cm.2 秒。我们认为，原生质通过外原生质膜与细胞壁分离，在该膜处向外的钠运输维持细胞内部的高K/Na比率，并通过液泡膜与液泡分离，在该处向内的氯运输维持高液泡氯离子。液泡膜似乎是细胞主要扩散阻力的部位，但外原生质膜可能是电位的主要部分。
The distribution and rates of exchange of the ions sodium, potassium, and chloride in single internodal cells of the ecorticate characean, Nitellopsis obtusa, have been studied. In tracer experiments three kinetic compartments were found, the outermost "free space" of the cell, a compartment we have called "protoplasmic non-free space", and the cell sap. The concentrations in the vacuole were 54 mM Na+, 113 mM K+, and 206 mM Cl-. The steady state fluxes across the vacuolar membrane were 0.4 pmole Na+/cm.2 sec., 0.25 pmole K+/cm.2 sec., and 0.5 pmole Cl-/cm.2 sec. The protoplasmic Na/K ratio is equal to that in the vacuole but protoplasmic chloride is relatively much lower. Osmotic considerations suggest a layer 4 to 6 µ thick with sodium and potassium concentrations close to those in the vacuole. The fluxes between protoplasm and external solution were of the order of 8 pmoles Na+/cm.2 sec. and 4 pmoles K+/cm.2 sec. We suggest that the protoplasm is separated from the cell wall by an outer protoplasmic membrane at which an outward sodium transport maintains the high K/Na ratio of the cell interior, and from the vacuole by the tonoplast at which an inward chloride transport maintains the high vacuolar chloride. The tonoplast appears to be the site of the principal diffusion resistance of the cell, but the outer protoplasmic membrane probably of the main part of the potential.