Control of ion distribution in isolated smooth muscle cells. I. Potassium.
Control of ion distribution in isolated smooth muscle cells. I. Potassium.
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DOI：
10.1085/jgp.75.2.163
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发表时间：
1980-02
期刊：
影响因子：
--
通讯作者：
Fay FS
中科院分区：
文献类型：
--
作者：
Scheid CR;Fay FS
我们描述了一种技术，用于检查单向离子运动的悬浮液中的酶分解平滑肌细胞来自蟾蜍的胃肌肉。该技术已用于分析42 K在这些细胞中的移动。分离后，细胞相对于K+分布处于稳定状态，这一发现大大简化了该分析。分离的细胞的钾含量是相同的那些完整的平滑肌（131 mM/升细胞内液）和稳定超过4小时，此外，单向流入和流出率是相等的。一个额外的简化提供的发现，几乎所有的K+交换的方式预测一个简单的两室系统组成的细胞外和细胞内的空间。在室温下，这些细胞的跨膜K+通量平均为1.2pmol.cm-2.s-1。一个大部分（约80%）的42 K流入似乎是由一个饱和的运输系统介导的表观Km为0.6 mM和表观Vmax为1.3 pmol.cm-2.s-1。假设膜电位为-50 mV，在这些分离的平滑肌细胞中计算的静息膜对K+的渗透性为2.9 × 10（-8）cm/s。计算的gK+为2.7 mumho/cm 2，仅构成电生理学测量的总膜电导的一小部分。后者的发现表明，在分离的细胞中的静息膜电位必须由除了K+离子。我们建议，这些方法研究平滑肌中的离子运动应有助于解开负责控制离子分布在休息，在本研究中，以及在响应神经递质的机制。
We describe a technique for examining unidirectional ion movements in suspensions of enzymatically disaggregated smooth muscle cells derived from stomach muscle of the toad. This technique has been used to analyze the movement of 42K across these cells. This analysis was greatly simplified by the finding that the cells were in a steady state with respect to K+ distribution after isolation. The potassium contents of the isolated cells were identical to those of intact smooth muscle (131 mM/liter intracellular fluid) and stable for over 4 h; moreover, the unidirectional influx and efflux rates were equal. An additional simplification was provided by the finding that virtually all the K+ exchanges in a manner predicted for a simple two-compartment system consisting of an extracellular and an intracellular space. Transmembrane K+ flux in these cells averaged 1.2 pmol.cm-2.s-1 at room temperature. A large portion (approximately 80%) of 42K influx appeared to be mediated by a saturable transport system with an apparent Km of 0.6 mM and an apparent Vmax of 1.3 pmol.cm-2.s-1. The calculated resting membrane permeability to K+ in these isolated smooth muscle cells, assuming a membrane potential of -50 mV, was 2.9 X 10(-8) cm/s. The calculated gK+ was 2.7 mumho/cm2 constituting only a small fraction of the total membrane conductance as measured electrophysiologically. The latter finding suggests that the resting membrane potential in the isolated cells must be determined by ions in addition to K+. We propose that these methods for studying ion movements in smooth muscle should aid in unraveling the mechanisms responsible for controlling the distribution of ions both at rest, as in the present study, as well as in response to neurotransmitters.