American Journal of Physiology-Legacy Content · 1964 · 402 citations · 26 references
MedicineNephrologyPhysiologyExcretionMineral MetabolismRenal PathophysiologyPotassium HomeostasisRenal ExcretionRenal Mineral HandlingRenal PhysiologyTubular ReabsorptionUrinary ExcretionDistal Tubule ReabsorptionLow-sodium DietPotassium ReabsorptionProximal Tubule PhysiologyProximal Tubule ReabsorptionRenal Potassium HandlingTubular ExcretionUrinary Potassium Excretion
The study collected proximal and distal tubular fluid from rats on control, low‑K, or high‑K, low‑Na diets, administered inulin‑C^14, and measured Na and K concentrations by dual‑channel microflame photometry and radioactivity, while transtubular electrical potentials were recorded with glass microelectrodes. Proximal tubular K TF/P ratios were slightly below unity in all groups, whereas distal tubules exhibited net K secretion into the lumen in control and high‑K, low‑Na animals, continued reabsorption in low‑K animals, and K entry driven by an electrochemical gradient.
Samples of proximal and distal tubular fluid were collected from rats maintained on a control, a low-K, or a high-K, low-Na diet. All animals received inulin-C 14 . Plasma (P) and tubular fluid (TF) were analyzed for Na and K by dual-channel microflame photometry and assayed for radioactivity. Transtubular electrical potential differences were measured by means of glass microelectrodes. Mean TF/P ratios for potassium in the proximal tubule were slightly below unity in all groups of animals. A comparison of the relative increase in K and inulin-C 14 along the distal tubule indicates: 1) net movement of potassium into the tubular lumen in most control animals; 2) net movement of K into the tubular lumen of high-K, low-Na, sulfate-loaded animals, and in dichlorphenamide-treated animals on a control diet; and 3) the possibility of continued net reabsorption of potassium along the distal tubule and, particularly, the collecting duct in animals kept on a low-K diet. Distal tubular entry of potassium occurs down an electrochemical potential gradient.
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