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Journal Article

Axial heterogeneity of sodium-bicarbonate cotransport in proximal straight tubule of rabbit kidney


Frömter,  Eberhard
Department of Physiology, Max Planck Institute of Biophysics, Max Planck Society;

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Kondo, Y., & Frömter, E. (1987). Axial heterogeneity of sodium-bicarbonate cotransport in proximal straight tubule of rabbit kidney. Pflügers Archiv: European Journal of Physiology, 410(4-5), 481-486. doi:10.1007/BF00586529.

Cite as: https://hdl.handle.net/21.11116/0000-0008-2DB9-6
Intracellular microelectrodes were used to investigate rheogenic Na+ (HCO3-)n cotransport in different segments of isolated proximal straight tubule (PST) of rabbit kidney. In the first portion (S2 segment) the peritubular cell membrane potential Vb averaged -46.0, SE ± 1.3 mV (n = 20), while in terminal portion (S3 segment) it averaged -68.3, SE ± 2.5 mV (n = 10). This difference may reflect different modes of anion permeation across the peritubular cell membrane. In S2 segments, sudden 10:1 reduction of bath HCO3- concentration caused a fast transient cell depolarization, delta Vb = -45.8, SE ± 1.2 mV (n = 33) as expected from the presence of Na+ (HCO3-)n cotransport. As the puncture site moved further distally, delta Vb declined and gradually changed its time course by superposition of a slower secondary depolarization. In this region the transient cell depolarization could be recuperated by inhibiting the peritubular K+ conductance with Ba2+ (1 mmol/l). In S3 segments, however, the HCO3--dependent transient cell depolarization was completely lost both in the absence and presence of Ba2+. In addition, sudden reduction of bath Na+ concentration did not acidify the cell, as it did in the S2 segment. The data indicate that the expression of Na+ (HCO3-)n cotransport in the peritubular cell membrane gradually diminishes towards the end of the S2 segment and is lost in the S3 segment.