Welsh M J
Am J Physiol. 1983 Jun;244(6):F639-45. doi: 10.1152/ajprenal.1983.244.6.F639.
Addition of barium ion, Ba2+, to the submucosal bathing solution of canine tracheal epithelium reversibly decreased the short-circuit current and increased transepithelial resistance. The decrease in short-circuit current represented a decrease in the net rate of Cl secretion with no change in the rate of Na absorption. Intracellular microelectrode techniques and an equivalent electrical circuit analysis were used to localize the effect of Ba2+ to an inhibition of the permeability of the basolateral membrane to K. Ba2+ (2 mM) doubled basolateral membrane resistance, decreased the equivalent electromotive force at the basolateral membrane, and decreased the magnitude of the depolarization of basolateral membrane voltage produced by increasing the submucosal K concentration. The inhibition of the basolateral K permeability depolarized the negative intracellular voltage, resulting in both a decrease in the driving force for Cl exit and an estimated increase in intracellular Cl concentration. These studies indicate that there is a Ba2+-inhibitable K conductance at the basolateral membrane of tracheal epithelial cells and that the K permeability plays an important role in the generation of the negative intracellular electrical potential that provides the driving force for Cl exit from the cell.
向犬气管上皮的黏膜下灌流液中添加钡离子（Ba2+）会使短路电流可逆性降低，并增加跨上皮电阻。短路电流的降低代表着氯离子分泌净速率的下降，而钠离子吸收速率没有变化。采用细胞内微电极技术和等效电路分析方法，将Ba2+的作用定位为抑制基底外侧膜对钾离子的通透性。2 mM的Ba2+使基底外侧膜电阻增加一倍，降低了基底外侧膜的等效电动势，并减小了因黏膜下钾离子浓度升高而产生的基底外侧膜电压去极化幅度。基底外侧钾离子通透性的抑制使细胞内负电压去极化，导致氯离子外流驱动力降低，并使细胞内氯离子浓度估计值升高。这些研究表明，气管上皮细胞的基底外侧膜存在一种可被Ba2+抑制的钾离子电导，并且钾离子通透性在产生细胞内负电位中起重要作用，该负电位为氯离子从细胞中流出提供驱动力。
