Rae J L, Dewey J, Cooper K
Department of Physiology, Mayo Foundation, Rochester, MN 55905.
Exp Eye Res. 1989 Oct;49(4):591-609. doi: 10.1016/s0014-4835(89)80057-0.
The corneal endothelium from several species contains a highly conductive, flickery potassium selective channel in the apical membrane. The channel flicker is not due to blockade. The single channel has an inwardly rectifying current-voltage relationship under symmetrical ionic conditions. Based on reversal potential measurements, it is more than 40:1 selective for potassium over sodium. It also shows subconductance levels. In bathing solutions lacking chloride and bicarbonate, its open probability is less than 0.1 and is quite independent of voltage in the physiological voltage range. Bicarbonate in the bath or DIDs in the pipette increase channel activity. The channel is blocked by external cesium in the 0.5 to 5 mM range. The steepness of the voltage dependence of this blockade is consistent with multiple occupancy.
几种物种的角膜内皮细胞在顶端膜中含有一种高导电性、闪烁的钾选择性通道。通道闪烁并非由于阻断所致。在对称离子条件下，单通道具有内向整流的电流-电压关系。基于反转电位测量，其对钾的选择性比对钠高40倍以上。它还表现出亚电导水平。在缺乏氯离子和碳酸氢根离子的浴液中，其开放概率小于0.1，并且在生理电压范围内与电压相当独立。浴液中的碳酸氢根离子或移液管中的DIDs会增加通道活性。该通道在0.5至5 mM范围内被外部铯阻断。这种阻断的电压依赖性的陡峭程度与多重占据一致。
