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

K. Matsuzaki, J. B. Stokes, Victor L. Schuster

Research output: Contribution to journalArticle

15 Citations (Scopus)

Abstract

In rabbit cortical collecting duct, Cl- self exchange accounts for most of the transepithelial Cl- tracer rate coefficient, K(Cl) (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 K(Cl). Addition of 0.5% CO2 to a HEPES bath (final pH = 7.24) stimulated K(Cl) by 70 ± 19 nm/s, a ΔK(Cl) 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 (pH(i)) and HCO3- concentration were examined by clamping pH(i) using high K+ and nigericin. Increasing pH(i) from 6.9 to 7.6 in solutions without exogenous CO2 or HCO3- increased K(Cl) by 71 ± 17 nm/s. These results suggest that pH(i) might regulate anion exchange. However, during such a pH(i)-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 (pH(i) clamped at 6.9). With this increase in [HCO3-](i) at constant pH(i), K(Cl) 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. Although pH(i) may also have an effect on the anion exchange process, under the present conditions, the HCO3- effect seems to be more potent and is evident at low concentrations of HCO3- and CO2.

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Cell Physiology
Volume257
Issue number1
StatePublished - 1989
Externally publishedYes

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Ducts
Anions
Rabbits
Nigericin
HEPES
Experiments
Baths
ethane sulfonate
Constriction

ASJC Scopus subject areas

  • Cell Biology
  • Clinical Biochemistry
  • Physiology

Cite this

Stimulation of Cl- self exchange by intracellular HCO3- in rabbit cortical collecting duct. / Matsuzaki, K.; Stokes, J. B.; Schuster, Victor L.

In: American Journal of Physiology - Cell Physiology, Vol. 257, No. 1, 1989.

Research output: Contribution to journalArticle

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abstract = "In rabbit cortical collecting duct, Cl- self exchange accounts for most of the transepithelial Cl- tracer rate coefficient, K(Cl) (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 K(Cl). Addition of 0.5{\%} CO2 to a HEPES bath (final pH = 7.24) stimulated K(Cl) by 70 ± 19 nm/s, a ΔK(Cl) 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 (pH(i)) and HCO3- concentration were examined by clamping pH(i) using high K+ and nigericin. Increasing pH(i) from 6.9 to 7.6 in solutions without exogenous CO2 or HCO3- increased K(Cl) by 71 ± 17 nm/s. These results suggest that pH(i) might regulate anion exchange. However, during such a pH(i)-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 (pH(i) clamped at 6.9). With this increase in [HCO3-](i) at constant pH(i), K(Cl) 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. Although pH(i) may also have an effect on the anion exchange process, under the present conditions, the HCO3- effect seems to be more potent and is evident at low concentrations of HCO3- and CO2.",
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