Regulation of Na+ channels by luminal Na+ in rat cortical collecting tubule. Academic Article uri icon

Overview

abstract

  • 1. The idea that luminal Na+ can regulate epithelial Na+ channels was tested in the cortical collecting tubule of the rat using whole-cell and single-channel recordings. Here we report results consistent with the idea of Na+ self-inhibition. 2. Macroscopic amiloride-sensitive currents (INa) were measured by conventional whole-cell clamp. INa was a saturable function of external Na+ concentration ([Na+]o) with an apparent Km of 9 mM. Single channel currents (iNa) were measured in cell-attached patches. iNa increased with pipette Na+ concentration with an apparent Km of 48 mM. Since INa = (iNa)NPo, the different Km values imply that the channel density (N) and/or open probability (Po) increase as [Na+]o decreases. Reduction of [Na+]o after increasing intracellular Na+ concentration also increased the outward amiloride-sensitive conductance, consistent with activation of the Na+ channels. 3. The underlying mechanism was studied by changing pipette Na+ concentration while recording from cell-attached patches. No increase in NPo was observed, suggesting that the effect is not a direct interaction between [Na+]o and the channel. 4. [Na+]o was varied outside the patch-clamp pipette while recording from cell-attached patches. When amiloride was in the bath to prevent Na+ entry, no change in NPo was observed. 5. Activation of the channels by hyperpolarization was observed with 140 mM Na+o but not with 14 mM Na+o. 6. The results are consistent with the concept of self-inhibition of Na+ channels by luminal Na+. Activation of the channels by lowering [Na+]o is not additive with that achieved by hyperpolarization.

publication date

  • May 15, 1998

Research

keywords

  • Kidney Cortex
  • Kidney Tubules, Collecting
  • Sodium
  • Sodium Channels

Identity

PubMed Central ID

  • PMC2230952

Scopus Document Identifier

  • 0032523765

Digital Object Identifier (DOI)

  • 10.1085/jgp.107.1.35

PubMed ID

  • 9547389

Additional Document Info

volume

  • 509 ( Pt 1)

issue

  • Pt 1