Reuss L, Weinman S A, Grady T P
J Gen Physiol. 1980 Jul;76(1):33-52. doi: 10.1085/jgp.76.1.33.
A study of the mechanisms of the effects of amphotericin B and ouabain on cell membrane and transepithelial potentials and intracellular K activity (alpha Ki) of Necturus gallbladder epithelium was undertaken with conventional and K-selective intracellular microelectrode techniques. Amphotericin B produced a mucosa-negative change of transepithelial potential (Vms) and depolarization of both apical and basolateral membranes. Rapid fall of alpha Ki was also observed, with the consequent reduction of the K equilibrium potential (EK) across both the apical and the basolateral membrane. It was also shown that, unless the mucosal bathing medium is rapidly exchanged, K accumulates in the unstirred fluid layers near the luminal membrane generating a paracellular K diffusion potential, which contributes to the Vms change. Exposure to ouabain resulted in a slow decrease of alpha Ki and slow depolarization of both cell membranes. Cell membrane potentials and alpha Ki could be partially restored by a brief (3-4 min) mucosal substitution of K for Na. Under all experimental conditions (control, amphotericin B, and ouabain), EK at the basolateral membrane was larger than the basolateral membrane equivalent emf (Eb). Therefore, the K chemical potential difference appears to account for Eb and the magnitude of the cell membrane potentials, without the need to postulate an electrogenic Na pump. Comparison of the rate of Na transport across the tissue with the electrodiffusional K flux across the basolateral membrane indicates that maintenance of a steady-state alpha Ki cannot be explained by a simple Na,K pump-K leak model. It is suggested that either a NaCl pump operates in parallel with the Na,K pump, or that a KCl downhill neutral extrusion mechanism exists in addition to the electrodiffusional K pathway.
运用传统的和钾选择性细胞内微电极技术，对两性霉素B和哇巴因对美西螈胆囊上皮细胞膜、跨上皮电位以及细胞内钾活性（αKi）的影响机制进行了研究。两性霉素B使跨上皮电位（Vms）出现黏膜阴性变化，并使顶端膜和基底外侧膜发生去极化。还观察到αKi迅速下降，随之顶端膜和基底外侧膜的钾平衡电位（EK）降低。研究还表明，除非迅速更换黏膜浴液，钾会在靠近管腔膜的未搅动液层中蓄积，产生细胞旁钾扩散电位，这对Vms变化有影响。暴露于哇巴因会导致αKi缓慢下降以及两个细胞膜缓慢去极化。短暂（3 - 4分钟）用钾替代黏膜中的钠可使细胞膜电位和αKi部分恢复。在所有实验条件下（对照、两性霉素B和哇巴因），基底外侧膜的EK大于基底外侧膜等效电动势（Eb）。因此，钾的化学势差似乎可解释Eb和细胞膜电位的大小，无需假定存在电生性钠泵。比较组织中钠转运速率与基底外侧膜上钾的电扩散通量表明，简单的钠钾泵 - 钾渗漏模型无法解释αKi稳态的维持。有人提出，要么是一个氯化钠泵与钠钾泵并行运作，要么是除了钾的电扩散途径外，还存在一种氯化钾下坡中性排出机制。
