Regulation of renal Na+,K(+)-ATPase in rat thick ascending limb during K+ depletion: evidence for modulation of Na+ affinity

• Published in: The Journal of physiology 1996-02, Vol.490 (Pt 3), p.623-632
• Main Authors: B Buffin-Meyer, S Marsy, C Barlet-Bas, L Cheval, M Younes-Ibrahim, R Rajerison, A Doucet
• Format: Article
• Language: English
• Subjects: Animals; Dose-Response Relationship, Drug; Kidney; Kidney - metabolism; Life Sciences; Male; Potassium; Potassium - metabolism; Rats; Rats, Wistar; Sodium; Sodium - pharmacology; Sodium-Potassium-Exchanging ATPase; Sodium-Potassium-Exchanging ATPase - physiology; Time Factors
• ISSN: 0022-3751; 1469-7793
• DOI: 10.1113/jphysiol.1996.sp021172

1. NaCl reabsorption along the loop of Henle is reduced in K(+)-depleted rats. Because Na+,K(+)-ATPase energizes this transport and because K+ depletion is known to induce an upregulation of Na+,K(+)-ATPase in most tissues, the regulation of this enzyme was investigated at the level of single thick ascending limbs of the loop of Henle freshly microdissected from rats fed either a normal (control rats) or a low-K+ diet (LK rats). 2. Within 2 weeks of K+ depletion, Na+,K(+)-ATPase activity and [3H]ouabain binding were increased by 30-50% in the medullary portion of the thick ascending limb (MTAL). 3. Despite this increase in the number of Na+,K(+)-ATPase units, the transport capacity of the Na+,K+ pump, determined by ouabain-sensitive Rb+ uptake in the presence of an extracellular concentration of Rb+ mimicking the kalaemia determined in control (4.0 mM Rb+) and LK rats (2.3 mM Rb+), was reduced in MTAL from LK rats. 4. Inhibition of the Na+,K+ pump was not accounted for by changes in either extracellular K+ or intracellular Na+ concentrations, but by a decrease in the pump affinity for Na+. 5. Because this change in the apparent affinity of the Na+,K+ pump for Na+ was detectable in intact but not in permeabilized MTAL cells, it is probably induced by a rapidly reversible cytosolic factor.