Ebata S, Muto S, Asano Y
Department of Nephrology, Jichi Medical School, Tochigi, Japan.
J Clin Invest. 1992 Oct;90(4):1547-57. doi: 10.1172/JCI116023.
Microelectrode techniques were used to determine the Na+ and K+ transport properties of the collecting duct cell in the isolated cortical collecting duct (CCD) from rabbits 14 d after uninephrectomy (UNX); results were compared with those from sham-operated rabbits (control). UNX had no effects on plasma aldosterone levels. The CCDs from UNX rabbits exhibited structural hypertrophy. The lumen negative transepithelial voltage and the basolateral membrane voltage (VB) were elevated in the UNX group. Although the transepithelial conductance (GT) and the fractional apical membrane resistance (fRA) were not different between the two groups, the conductances of the apical and the basolateral membranes were increased, and the tight junction conductance was decreased in the UNX group. The amiloride-sensitive changes in apical membrane voltage (VA), fRA, and GT were greater in the UNX group. The changes in VA upon raising the perfusate K+ concentration and the changes in VA and GT upon addition of Ba2+ to the perfusate were elevated in the UNX group. Upon raising K+ in the bath, a large depolarization of VB was observed in the UNX group. Lowering the bath Cl- resulted in a small depolarization of VB in the UNX group. Addition of Ba2+ to the bath in the UNX group caused the VB to hyperpolarize in parallel with decreases in GT and fRA whereas in the control group it had no effect on VB. Addition of ouabain to the bath resulted in a large depolarization of VB in the UNX group. We conclude that (a) UNX stimulates conductances of Na+ and K+ in the apical membrane, active Na(+)-K+ pump activity, and K+ conductance in the basolateral membrane, independently of plasma aldosterone; (b) The basolateral membrane in the tubules of UNX rabbits is more selective to K+; and (c) the hyperpolarization of VB upon UNX may increase passive K+ entry into the cell across the basolateral membrane.
采用微电极技术测定了单侧肾切除（UNX）14天后兔离体皮质集合管（CCD）中集合管细胞的钠钾转运特性；并将结果与假手术兔（对照组）进行比较。UNX对血浆醛固酮水平无影响。UNX兔的CCD出现结构肥大。UNX组管腔负跨上皮电压和基底外侧膜电压（VB）升高。虽然两组之间的跨上皮电导（GT）和顶端膜电阻分数（fRA）无差异，但UNX组顶端膜和基底外侧膜的电导增加，紧密连接电导降低。UNX组顶端膜电压（VA）、fRA和GT对氨氯地平敏感的变化更大。在灌注液中提高钾浓度时VA的变化以及在灌注液中添加Ba2+时VA和GT的变化在UNX组中升高。在浴液中提高钾浓度时，UNX组观察到VB出现大的去极化。降低浴液中的Cl-导致UNX组VB出现小的去极化。在UNX组的浴液中添加Ba2+导致VB超极化，同时GT和fRA降低，而在对照组中对VB无影响。在浴液中添加哇巴因导致UNX组VB出现大的去极化。我们得出结论：（a）UNX刺激顶端膜中钠和钾的电导、钠钾主动泵活性以及基底外侧膜中的钾电导，与血浆醛固酮无关；（b）UNX兔肾小管中的基底外侧膜对钾更具选择性；（c）UNX后VB的超极化可能增加钾通过基底外侧膜被动进入细胞。
