Rae J L, Dewey J, Rae J S, Nesler M, Cooper K
Department of Physiology, Mayo Foundation, Rochester, Minnesota 55905.
Invest Ophthalmol Vis Sci. 1990 Sep;31(9):1799-809.
The basal cell layers of the rabbit and human corneal epithelia contain a frequently occurring ionic channel whose unitary currents can be recorded in cell-attached or excised membrane patches by use of a patch voltage clamp. The channel is highly conductive (165 pS in 150 mM K+ salts) and is very selective for K+ over Na+ (PK/PNa greater than 40:1). Its open probability is increased by the application of suction to the recording pipette although its gating is less sensitive to suction than that of many other "stretch-activated" channels reported. The current through the channel is a saturating function of the K+ concentration in the bathing solutions with half saturation occurring at 480 mM and a single-channel current at saturation (imax) of 31 pA. In the absence of applied suction, the open probability is extremely variable from patch to patch and shows little voltage dependence over the physiologic voltage range. The channel also gates frequently to several subconductance levels. It is blocked by external Cs+ and Ba+2 in the 0.1-10 mM range but not by most other K+ channel blockers. It is also partially blocked by Ca+2 at both its internal and external surfaces. Because of its novel properties (stretch activation and large conductance), it can be used to measure the input resistance and total capacitance of single dissociated cells.
兔和人角膜上皮的基底细胞层含有一种常见的离子通道，通过膜片钳技术可在细胞贴附或切除的膜片上记录其单通道电流。该通道具有高导电性（在150 mM K⁺盐中为165 pS），对K⁺的选择性远高于Na⁺（PK/PNa大于40:1）。尽管其门控对吸力的敏感性低于许多其他报道的“牵张激活”通道，但向记录微管施加吸力会增加其开放概率。通过该通道的电流是浴液中K⁺浓度的饱和函数，半饱和浓度为480 mM，饱和时的单通道电流（imax）为31 pA。在未施加吸力时，不同膜片的开放概率变化极大，且在生理电压范围内几乎没有电压依赖性。该通道还经常门控到几个亚电导水平。它在0.1 - 10 mM范围内被外部Cs⁺和Ba²⁺阻断，但不被大多数其他K⁺通道阻滞剂阻断。它在其内外表面也被Ca²⁺部分阻断。由于其独特的性质（牵张激活和大电导），它可用于测量单个解离细胞的输入电阻和总电容。
