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

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.