氯离子在无钠溶液中的电扩散运动：培养心肌细胞中一种可能的钙激活氯电导。

Electrodiffusive movements of chloride ion in sodium-free solution: a possible calcium activated chloride conductance in cultured heart cells.

作者信息

Liu S, Lieberman M

机构信息

Department of Cell Biology, Duke University Medical Center, Durham, North Carolina.

出版信息

Cardiovasc Res. 1994 Nov;28(11):1629-34. doi: 10.1093/cvr/28.11.1629.

DOI:10.1093/cvr/28.11.1629

PMID:7842455

Abstract

OBJECTIVE

The aim was to demonstrate that removal of extracellular sodium (Na+o), a manoeuvre known to increase intracellular calcium (Cai2+), can activate a chloride ion conductance in cultured embryonic chick heart cells.

METHODS

Intracellular chloride activity (aiCl) and membrane potentials (Em) were simultaneously measured using chloride selective and 3 M KCl filled microelectrodes.

RESULTS

In Na+o-free and K+o-free solutions, a frusemide (0.3 mM) resistant decrease in aiCl of 10 mM was recorded within 10 min, along with a 5 mV hyperpolarisation, and the calculated chloride equilibrium potential (ECl) followed the change of Em, suggesting a possibly enhanced chloride conductance. When cells were exposed to Na+o-free solution, the decrease of aiCl by approximately 10 mM was associated with an initial depolarisation, followed by a hyperpolarisation to approximately -60 mV (more negative than ECl). Subsequent removal of K+o depolarised Em to -39 mV (approximately ECl), and no further loss of aiCl occurred. Restoration of K+o caused a hyperpolarisation of Em (more negative than ECl) and a continuing decline of aiCl. Prevention of K+o induced hyperpolarisation by addition of 1 mM Ba2+ stopped the decline of aiCl (Em approximately ECl), suggesting that following Na+o removal, alteration of the driving force for chloride led to a chloride efflux via an enhanced chloride conductance. When Em depolarised to -50 mV after 3 min exposure to 0.1 mM ouabain, removal of [Cl-]o caused a further depolarisation and readdition of [Cl-]o induced an 18 mV hyperpolarisation. This chloride induced hyperpolarisation was blocked by removal of [Ca2+]o (+1 mM EGTA).

CONCLUSIONS

The increase in chloride conductance observed under conditions that are known to raise Ca2+i supports the presence of a Ca2+i activated chloride conductance in cultured chick heart cells.

摘要

目的

旨在证明去除细胞外钠（Na⁺ₒ）这一已知可增加细胞内钙（Ca²⁺ᵢ）的操作，能够激活培养的胚胎鸡心脏细胞中的氯离子电导。

方法

使用氯离子选择性微电极和充满3 M KCl的微电极同时测量细胞内氯离子活性（aᵢCl）和膜电位（Eₘ）。

结果

在无Na⁺ₒ和无K⁺ₒ的溶液中，10分钟内记录到呋塞米（0.3 mM）抵抗性的aᵢCl下降10 mM，同时伴有5 mV的超极化，计算得出的氯离子平衡电位（ECl）随Eₘ变化，提示氯离子电导可能增强。当细胞暴露于无Na⁺ₒ溶液时，aᵢCl下降约10 mM与初始去极化相关，随后超极化至约 -60 mV（比ECl更负）。随后去除K⁺ₒ使Eₘ去极化至 -39 mV（约为ECl），且aᵢCl不再进一步下降。恢复K⁺ₒ导致Eₘ超极化（比ECl更负）且aᵢCl持续下降。通过添加1 mM Ba²⁺防止K⁺ₒ诱导的超极化可阻止aᵢCl下降（Eₘ约为ECl），表明去除Na⁺ₒ后，氯离子驱动力的改变导致氯离子通过增强的氯离子电导外流。当暴露于0.1 mM哇巴因3分钟后Eₘ去极化至 -50 mV时，去除[Cl⁻]ₒ导致进一步去极化，重新添加[Cl⁻]ₒ诱导18 mV超极化。这种氯离子诱导的超极化被去除[Ca²⁺]ₒ（+1 mM EGTA）阻断。