Laboratory of Veterinary Pharmacology, Research Institute of Veterinary Science, College of Veterinary Medicine, Seoul National University, 599 Gwanak-Ro, Gwanak-Gu, Seoul 151-742, Republic of Korea.
J Membr Biol. 2011 Feb;239(3):167-75. doi: 10.1007/s00232-010-9335-5. Epub 2010 Dec 14.
The primo-vascular (Bonghan) tissue has been identified in most tissues in the body, but its structure and functions are not yet well understood. We characterized electrophysiological properties of the cells of the primo-nodes (PN) on the surface of abdominal organs using a slice patch clamp technique. The most abundant were small round cells (~10 μm) without processes. These PN cells exhibited low resting membrane potential (-36 mV) and did not fire action potentials. On the basis of the current-voltage (I-V) relationships and kinetics of outward currents, the PN cells can be grouped into four types. Among these, type I cells were the majority (69%); they showed strong outward rectification in I-V relations. The outward current was activated rapidly and sustained without decay. Tetraethylammonium (TEA) dose-dependently blocked both outward and inward current (IC(50), 4.3 mM at ± 60 mV). In current clamp conditions, TEA dose-dependently depolarized the membrane potential (18.5 mV at 30 mM) with increase in input resistance. The tail current following a depolarizing voltage step was reversed at -27 mV, and transient outward current like A-type K(+) current was not expressed at holding potential of -80 mV. Taken together, the results demonstrate for the first time that the small round PN cells are heterogenous, and that, in type I cells, TEA-sensitive current with limited selectivity to K(+) contributed to resting membrane potential of these cells.
初级血管（Bonghan）组织已在体内大多数组织中被识别出来，但它的结构和功能尚未得到很好的理解。我们使用切片膜片钳技术研究了腹部器官表面初级节点（PN）细胞的电生理特性。最丰富的是没有突起的小圆形细胞（~10μm）。这些 PN 细胞表现出低的静息膜电位（-36 mV），不产生动作电位。基于电流-电压（I-V）关系和外向电流的动力学，PN 细胞可以分为四种类型。其中，I 型细胞占多数（69%）；它们在 I-V 关系中表现出强烈的外向整流。外向电流快速激活并持续，没有衰减。四乙铵（TEA）剂量依赖性地阻断外向和内向电流（IC50 在 ±60 mV 时为 4.3 mM）。在电流钳条件下，TEA 剂量依赖性地使膜电位去极化（30 mM 时为 18.5 mV），同时增加输入电阻。在去极化电压阶跃后的尾电流在-27 mV 处反转，并且在 -80 mV 的保持电位下不表达类似于 A 型 K(+)电流的瞬态外向电流。总之，这些结果首次表明，小圆形 PN 细胞是异质的，在 I 型细胞中，TEA 敏感的电流对 K(+)的选择性有限，对这些细胞的静息膜电位有贡献。
