Stimulation of Cl- self exchange by intracellular HCO3- in rabbit cortical collecting duct

Am J Physiol. 1989 Jul;257(1 Pt 1):C94-101. doi: 10.1152/ajpcell.1989.257.1.C94.

Abstract

In rabbit cortical collecting duct, Cl- self exchange accounts for most of the transepithelial Cl- tracer rate coefficient, KCl (nm/s); a small fraction is effected by Cl--HCO3- exchange and Cl- diffusion. We previously reported that changing from a CO2-free N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES) bath to a 5% CO2-25 mM HCO3- bath stimulates Cl- self exchange. Here, we examine in further detail the individual components of the CO2-HCO3- system that stimulate KCl. Addition of 0.5% CO2 to a HEPES bath (final pH = 7.24) stimulated KCl by 70 +/- 19 nm/s, a delta KCl comparable to that induced by 1% CO2 (pH 7.12), 6% CO2 (pH 6.6), or 6% CO2-25 mM HCO3- (pH 7.4). The roles of intracellular pH (pHi) and HCO3- concentration were examined by clamping pHi using high K+ and nigericin. Increasing pHi from 6.9 to 7.6 in solutions without exogenous CO2 or HCO3- increased KCl by 71 +/- 17 nm/s. These results suggest that pHi might regulate anion exchange. However, during such a pHi-shift experiment, metabolically derived CO2 produces a concomitant change in intracellular HCO3- concentration [( HCO3-]i). To determine whether an increase in [HCO3-]i could stimulate Cl- self exchange, we replaced HEPES with 6% CO2-5 mM HCO3- isohydrically (pHi clamped at 6.9). With this increase in [HCO3-]i at constant pHi, KCl increased by 51 +/- 10 nm/s. These maneuvers had negligible effects on Cl- diffusion and Cl--HCO3- exchange. These experiments demonstrate that increases in cell [HCO3-] (or perhaps CO2) can stimulate transepithelial anion exchange.(ABSTRACT TRUNCATED AT 250 WORDS)

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Bicarbonates / metabolism
  • Bicarbonates / pharmacology*
  • Carbon Dioxide / pharmacology
  • Carrier Proteins / metabolism
  • Chloride-Bicarbonate Antiporters
  • Chlorides / metabolism*
  • Diffusion
  • Epithelium / metabolism
  • Hydrogen-Ion Concentration
  • Kidney Tubules / metabolism*
  • Kidney Tubules, Collecting / drug effects
  • Kidney Tubules, Collecting / metabolism*
  • Nigericin / pharmacology
  • Potassium / pharmacology
  • Rabbits
  • Sodium Cyanide / pharmacology

Substances

  • Bicarbonates
  • Carrier Proteins
  • Chloride-Bicarbonate Antiporters
  • Chlorides
  • Carbon Dioxide
  • Sodium Cyanide
  • Nigericin
  • Potassium