Suppr超能文献

伞藻中的离子通量:囊泡穿梭。

Ion fluxes in Acetabularia: vesicular shuttle.

作者信息

Mummert H, Gradmann D

机构信息

Institut für Biologie I der Universität, Tübingen, Germany.

出版信息

J Membr Biol. 1991 Dec;124(3):255-63. doi: 10.1007/BF01994358.

Abstract

Ion flux relations in the unicellular marine alga Acetabularia have been investigated by uptake and washout kinetics of radioactive tracers (22Na+, 42K+, 36Cl- and 86Rb+) in normal cells and in cell segments with altered compartmentation (depleted of vacuole or of cytoplasm). Some flux experiments were supplemented by simultaneous electrophysiological recordings. The main results and conclusions about the steady-state relations are: the plasmalemma is the dominating barrier for translocation of K+ with influx and efflux of about 100 nmol.m-2.sec-1. K+ passes three- to sevenfold more easily than Rb+ does. Under normal conditions, Cl- (the substrate of the electrogenic pump, which dominates the electrical properties of the plasmalemma in the resting state) shows two efflux components of about 17 and 2 mumol.m-2.sec-1, and a cytoplasmic as well as vacuolar [Cl-] of about 420 mM ([Cl-]o = 529 mM). At 4 degrees C, when the pump is inhibited, both influx and efflux, as well as the cellular [Cl-], are significantly reduced. Na+ ([Na+]i: about 70 mM, [Na+]o: 461 mM), which is of minor electrophysiological relevance compared to K+, exhibits rapid and virtually temperature-insensitive (electroneutral) exchange (two components with about 2 and 0.2 mumol.m-2.sec-1 for influx and efflux). Some results with Na+ and Cl- are inconsistent with conventional (noncyclic) compartmentation models: (i) equilibration of the vacuole (with the external medium) can be faster than equilibration of the cytoplasm, (ii) absurd concentration values result when calculated by conventional compartmental analysis, and (iii) large amounts of ions can be released from the cell without changes in the electrical potential of the cytoplasm. These observations can be explained by the particular compartmentation of normal Acetabularia cells (as known by electron micrographs) with about 1 part cytoplasm, 5 parts central vacuole, and 5 parts vacuolar vesicles. These vesicles communicate directly with the central vacuole, with the cytoplasm and with the external medium.

摘要

通过正常细胞以及分隔改变(液泡或细胞质缺失)的细胞片段对放射性示踪剂(22Na+、42K+、36Cl-和86Rb+)的摄取和洗脱动力学,研究了单细胞海洋藻类伞藻中的离子通量关系。一些通量实验通过同步电生理记录进行补充。关于稳态关系的主要结果和结论如下:质膜是K+转运的主要屏障,其流入和流出量约为100 nmol·m-2·sec-1。K+通过的难易程度比Rb+高三到七倍。在正常条件下,Cl-(生电泵的底物,在静息状态下主导质膜的电特性)显示出约17和2 μmol·m-2·sec-1的两个流出成分,细胞质和液泡中的[Cl-]约为420 mM([Cl-]o = 529 mM)。在4℃时,当泵被抑制时,流入和流出以及细胞内的[Cl-]都会显著降低。与K+相比,电生理相关性较小的Na+([Na+]i:约70 mM,[Na+]o:461 mM)表现出快速且几乎对温度不敏感的(电中性)交换(流入和流出的两个成分分别约为2和0.2 μmol·m-2·sec-1)。一些关于Na+和Cl-的结果与传统的(非循环)分隔模型不一致:(i)液泡(与外部介质)的平衡可能比细胞质的平衡更快,(ii)通过传统的分隔分析计算会得出荒谬的浓度值,(iii)大量离子可以从细胞中释放出来而细胞质的电位没有变化。这些观察结果可以通过正常伞藻细胞的特殊分隔来解释(如电子显微镜照片所示),其细胞质约占1份,中央液泡约占5份,液泡小泡约占5份。这些小泡直接与中央液泡、细胞质和外部介质相通。

文献AI研究员

20分钟写一篇综述,助力文献阅读效率提升50倍。

立即体验

用中文搜PubMed

大模型驱动的PubMed中文搜索引擎

马上搜索

文档翻译

学术文献翻译模型,支持多种主流文档格式。

立即体验