采用单电极电压钳技术在分离的美西螈肠上皮细胞中观察到两种钾电流。

Two types of potassium currents seen in isolated Necturus enterocytes with the single-electrode voltage-clamp technique.

作者信息

Valverde M A, Sheppard D N, Giraldez F, Sepúlveda F V

机构信息

Departamento de Bioquímica y Biología Molecular y Fisiología, Facultad de Medicina, Valladolid, Spain.

出版信息

J Physiol. 1991 Feb;433:645-61. doi: 10.1113/jphysiol.1991.sp018448.

DOI:10.1113/jphysiol.1991.sp018448

PMID:1841961

原文链接:https://pmc.ncbi.nlm.nih.gov/articles/PMC1181393/

Abstract

The ionic permeability of Necturus maculosus small intestine epithelial cells was investigated using intracellular microelectrodes to measure membrane potential in intact tissue or by the single-electrode voltage-clamp technique in isolated cells. 2. The basolateral membrane of enterocytes appears to be K+ selective as demonstrated by the dependence of membrane potential and fractional serosal resistance measured in the intact epithelium on serosal K+ concentration. 3. Isolated cells had membrane potentials similar to those measured in the intact tissue. Voltage-clamp experiments in a physiological Ringer solution showed the presence of both large outward and inward currents. 4. Removal of Cl- from the bathing medium, linear subtraction or the use of a Cl- channel blocker revealed outwardly rectifying currents. The quasi-linear component was also revealed following K+ channel inhibition; it reversed near ECl, suggesting that the charge carrier was Cl-. 5. Outwardly rectifying currents could be kinetically resolved into two components. A fast component (tau for activation < 4 ms) accounted for 60-80% of the total current at positive potentials. A slowly activating component appeared at voltages positive to 50 mV with tau for activation of > 25 ms. 6. The slow outward current showed strong voltage dependence of both activation and relaxation, which were faster at more depolarized potentials. 7. Both fast and slow outward currents seem to be carried by K+ as they were blocked by Ba2+ and tetraethylammonium (TEA). Tail current analysis of the slow component indicated a reversal potential very similar to EK. 8. Fast outward currents were half-activated at about -40 mV whereas slow outward currents were only apparent at more positive potentials. It is proposed that the fast outward K+ current plays a role, together with Cl- currents, in determining the resting membrane potential of Necturus enterocytes.

摘要

利用细胞内微电极测量完整组织中的膜电位，或通过单电极电压钳技术在分离细胞中研究了黄斑美西螈小肠上皮细胞的离子通透性。2. 肠上皮细胞的基底外侧膜似乎对K⁺具有选择性，这在完整上皮中测量的膜电位和浆膜电阻分数对浆膜K⁺浓度的依赖性中得到了证明。3. 分离的细胞具有与在完整组织中测量的膜电位相似的膜电位。在生理林格溶液中进行的电压钳实验显示存在大的外向和内向电流。4. 从浴液中去除Cl⁻、线性减法或使用Cl⁻通道阻滞剂揭示了外向整流电流。在K⁺通道抑制后也揭示了准线性成分；它在ECl附近反转，表明电荷载体是Cl⁻。5. 外向整流电流在动力学上可分解为两个成分。一个快速成分（激活时间常数<4毫秒）在正电位下占总电流的60-80%。一个缓慢激活的成分出现在高于50 mV的电压下，激活时间常数>25毫秒。6. 缓慢外向电流显示出激活和松弛的强烈电压依赖性，在更去极化的电位下更快。7. 快速和缓慢外向电流似乎都是由K⁺携带的，因为它们被Ba²⁺和四乙铵（TEA）阻断。缓慢成分的尾电流分析表明反转电位与EK非常相似。8. 快速外向电流在约-40 mV时被半激活，而缓慢外向电流仅在更正的电位下明显。有人提出，快速外向K⁺电流与Cl⁻电流一起在决定黄斑美西螈肠上皮细胞的静息膜电位中起作用。