Horisberger J D, Giebisch G
Yale University School of Medicine, Department of Physiology, New Haven, Connecticut 06510-8026.
J Gen Physiol. 1988 Nov;92(5):643-65. doi: 10.1085/jgp.92.5.643.
Membrane potentials and conductances, and intracellular ionic activities were studied in isolated perfused collecting tubules of K+-adapted Amphiuma. Intracellular Na+ (aNai) and K+ (aKi) activities were measured, using liquid ion-exchanger double-barreled microelectrodes. Apical and basolateral membrane conductances were estimated by cable analysis. The effects of inhibition of the apical conductance by amiloride (10(-5) M) and of inhibition of the basolateral Na-K pump by either a low K+ (0.1 mM) bath or by ouabain (10(-4) M) were studied. Under control conditions, aNai was 8.4 +/- 1.9 mM and aKi 56 +/- 3 mM. With luminal amiloride, aNai decreased to 2.2 +/- 0.4 mM and aKi increased to 66 +/- 3 mM. Ouabain produced an increase of aNai to 44 +/- 4 mM, and a decrease of aKi to 22 +/- 6, and similar changes were observed when the tubule was exposed to a low K+ bath solution. During pump inhibition, there was a progressive decrease of the K+-selective basolateral membrane conductance and of the Na+ permeability of the apical membrane. A similar inhibition of both membrane conductances was observed after pump inhibition by low K+ solution. Upon reintroduction of K+, a basolateral membrane hyperpolarization of -23 +/- 4 mV was observed, indicating an immediate reactivation of the electrogenic Na-K pump. However, the recovery of the membrane conductances occurred over a slower time course. These data imply that both membrane conductances are regulated according to the intracellular ionic composition, but that the basolateral K+ conductance is not directly linked to the pump activity.
在适应钾的美洲大鲵分离灌注的集合小管中研究了膜电位、电导和细胞内离子活性。使用液体离子交换双管微电极测量细胞内钠（aNai）和钾（aKi）活性。通过电缆分析估计顶端和基底外侧膜电导。研究了用氨氯地平（10^(-5) M）抑制顶端电导以及用低钾（0.1 mM）浴或哇巴因（10^(-4) M）抑制基底外侧钠钾泵的作用。在对照条件下，aNai为8.4±1.9 mM，aKi为56±3 mM。使用管腔氨氯地平后，aNai降至2.2±0.4 mM，aKi升至66±3 mM。哇巴因使aNai增加至44±4 mM，aKi降至22±6 mM，当小管暴露于低钾浴溶液时观察到类似变化。在泵抑制期间，钾选择性基底外侧膜电导和顶端膜钠通透性逐渐降低。在低钾溶液抑制泵后，观察到两种膜电导有类似抑制。重新引入钾后，观察到基底外侧膜超极化-23±4 mV，表明电生钠钾泵立即重新激活。然而，膜电导的恢复发生在较慢的时间进程中。这些数据表明，两种膜电导均根据细胞内离子组成进行调节，但基底外侧钾电导与泵活性没有直接联系。
