Cell sodium-induced recruitment of Na(+)-K(+)-ATPase pumps in rabbit cortical collecting tubules is aldosterone-dependent.

M Blot-Chabaud,F Wanstok,J P Bonvalet,N Farman

doi:10.1016/s0021-9258(19)38450-9

Abstract

The influence of intracellular sodium concentration ( [Na+]i) on the number of Na(+)-K(+)-ATPase pumps was examined in cortical collecting tubules (CCD) of kidneys from rabbits in different aldosterone conditions. Specific [3H]ouabain binding was measured in isolated CCD with various [Na+]i. Experiments were performed on adrenalectomized rabbits receiving only a substitutive dose of dexamethasone and on adrenalectomized rabbits replete with aldosterone. In aldosterone-replete rabbits, the number of binding sites increased linearly with [Na+]i, from 16 fmol/nl tubular volume at 15 mM Na+i to 39 fmol/nl tubular volume at 140 mM Na+i. Neither actinomycin D (5 microM) nor cycloheximide (10 microM) prevented this [Na+]i-dependent increase. In adrenalectomized rabbits, the number of ouabain-binding sites was reduced and did not increase with [Na+]i. These results are in favor of the presence of a "latent" pool of pumps in CCD, rapidly recruited under [Na+]i influence. Aldosterone appears to be required for the constitution and/or activation of this pool.

Highlights

From the Departement de Biologic, Znstitut National de la Sante et de la Recherche Mkdicale U246, Seruice Cellulaire, Centre d%tude Nucleaire de Sucluy, Gif-sur- Yuette 9il91, France de Siologie
In CCD, an aldosterone-sensitive transporting epithelium which precisely adjusts the final reabsorption of sodium in the kidney, aldosterone enhances transepithelial sodium transport by increasing both sodium entry via apical channels and basolateral sodium extrusion via Na’-K’-ATPase pumps [12,25]
Since one of the initial effects of aldosterone consists of an increase in sodium entry into cells [12, 26] and since very large and rapid changes in Na+-K+-ATPase activity occur in this epithelium [31], we examined the possibility that the recruitment of latent pumps at the basolateral membrane could be dependent on cell sodium

Summary

Introduction

From the Departement de Biologic, Znstitut National de la Sante et de la Recherche Mkdicale U246, Seruice Cellulaire, Centre d%tude Nucleaire de Sucluy, Gif-sur- Yuette 9il, France de Siologie. The influence of intracellular sodium concentration ([Na+]i) on the number of Na’-K+-ATPase pumps was examined in cortical collecting tubules (CCD) of kidneys from rabbits in different aldosterone conditions. Experiments were performed on adrenalectomized rabbits receiving only a substitutive dose of dexamethasone and on adrenalectomized rabbits replete with aldosterone. In aldosterone-replete rabbits, the number of binding sites increased linearly with [Na+]i, from 16 fmol/nl tubular volume at I5 mM Na+i to 39 fmol/nl tubular volume at I40 mM. Neither actinomycin D (5 MM) nor cycloheximide (10 FM) prevented this [NaQdependent increase. The number of ouabain-binding sites was reduced and did not increase with [Na+]i. Pool of pumps in CCD, rapidly recruited under [Na+]i influence. Aldosterone appears to be required for the constitution and/or activation of this pool

Methods

Results

Conclusion