Short-Term Effects of Uninephrectomy on Electrical Properties of the Cortical Collecting Duct from Rabbit Remnant Kidneys

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Abstract

Microelectrode techniques were used to assess the electrical properties of the collecting duct cell in the isolated perfused cortical collecting duct from remnant kidneys 3, 6, and 24 h after uninephrectomy (UNX); results were compared with those from sham-operated kidneys. Plasma aldosterone levels did not change during the time course after UNX. The lumen-negative transepithelial voltage was elevated significantly 3 h after UNX, and was increased further 24 h after UNX. The basolateral membrane voltage (VB) was elevated 6 h after UNX, and then was increased further at 24 h. Although the tight junction conductance and the fractional apical membrane resistance (fRA) were not altered at any time points after UNX, the apical membrane conductance as well as the transepithelial (GT) and basolateral membrane conductances increased 6 and 24 h after UNX. The changes in apical membrane voltage, GT, and fRA upon addition of luminal amiloride increased just 3 h after UNX, and then remained elevated at 6 and 24 h. The changes in apical membrane voltage and GT upon addition of luminal Ba2+, the changes in VB upon addition of bath ouabain, and the changes in VB, GT, and fRA upon raising bath K+ were not influenced 3 h after UNX, but increased at 6 and 24 h. At these latter periods after UNX, the transference number of Cl- of the basolateral membrane decreased significantly, whereas the transference number of K+ of the basolateral membrane increased significantly. Simultaneously, addition of Ba2+ to the bath caused the VB to hyperpolarize in parallel with decreases in GT and fRA. We conclude: (a) the initial effect of UNX (3 h) in the collecting duct cell is an increase in apical membrane Na+ conductance; (b) the delayed effects of UNX (6 and 24 h) are increases in apical membrane K+ conductance as well as basolateral membrane Na+ -K+ pump activity and K+ conductance; (c) the hyperpolarization of VB at 6 and 24 h after UNX may result in the decrease of the ratio of the relative Cl- conductance to the relative K+ conductance of the basolateral membrane and also may increase passive K+ entry into the cell across the basolateral membrane; (d) these time-dependent electrical changes occur independently of plasma aldosterone levels. (J. Clin. Invest. 1994. 93:286-296.) Key words: electrophysiology. sodium conductance. potassium conductance. sodium pump. uninephrectomy

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