title: Early effects of aldosterone on Na-K pump in rat cortical collecting tubules.
abstract: Sustained exposure to aldosterone (Aldo) increases the abundance and activity of the Na-K pump in cortical collecting tubules (CCT). However, the onset and mechanism of the early interaction of Aldo with the CCT pump, especially in adrenal-intact animals, are unclear. We evaluated the short-term effects of the hormone on Na-K-adenosinetriphosphatase (ATPase) activity and on ouabain-sensitive 86Rb uptake, a measure of the transporting rate of the pump, in microdissected CCT from adrenal-intact rats. Incubation with Aldo (10(-8) M, 2 h) had no effect on Na-K-ATPase activity (Vmax), whereas it produced at least a twofold increase in 86Rb uptake. This effect was generated by physiological concentrations of the hormone (threshold 10(-10) M; apparent K1/2 approximately 10(-9) M), after a short lag of less than or equal to 30 min. Incubation with Aldo in the presence of amiloride or nystatin or in a Na-free medium (choline chloride) did not prevent the enhanced 86Rb uptake seen after Aldo alone; possible interpretations of these observations are discussed. We conclude that Aldo produces a rapid stimulation of pump function in CCT that precedes its induction of new pump synthesis; the physiological significance of this effect is suggested by its occurrence in tubules from adrenal-intact animals within the time frame and concentration range of the hormone's effects on electrolyte transport.
authors.affiliation: Department of Medicine, University of Chicago Pritzker School of Medicine, Illinois 60637.
authors.forename: Y
authors.initials: Y
authors.lastname: Fujii
authors.forename: F
authors.initials: F
authors.lastname: Takemoto
authors.forename: A I
authors.initials: AI
authors.lastname: Katz
mesh_terms: D000450:Aldosterone / Q000494:pharmacology*; D000818:Animals; D007684:Kidney Tubules / Q000502:physiology*; D007685:Kidney Tubules, Collecting / Q000187:drug effects / Q000196:embryology / Q000502:physiology*; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D012414:Rubidium Radioisotopes; D015222:Sodium Channels / Q000187:drug effects / Q000502:physiology*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism / Q000502:physiology*
chemical_list: D015221:Potassium Channels; D012414:Rubidium Radioisotopes; D015222:Sodium Channels; D000450:Aldosterone; D000254:Sodium-Potassium-Exchanging ATPase