title: Potassium-sodium distribution in human lymphocytes: description by the association-induction hypothesis.
abstract: Human lymphocytes were equilibrated for 48 hours over a wide range of external potassium levels, and their contents of potassium, sodium, and water determined. As external potassium rose from zero, cell potassium rose steeply in a sigmoidal fashion, reached half-saturation at 0.4 mM esternal potassium, and then saturated at 129 mmoles/kg cells. The saturable cell potassium exchanged mole-for-mole with sodium. Analysis of the saturable components by a statistical-mechanical adsorption model demonstrated a cooperative intraction between sites determining equilibrium potassium-sodium distribution. Superimposed upon the saturable fraction of cell potassium was a smaller one that was non-saturable with increasing external potassium to at least 64 mM, and that, when expressed as mmoles/liter cell water, existed in a ratio to external potassium of 0.6. The results strongly support the association-induction hypothesis, which predicts a small non-saturable component of ions determined by exclusion from oriented cell water and a cooperative interaction between sites throughout the cell that associate with potassium or sodium.
mesh_terms: D000327:Adsorption; D002462:Cell Membrane / Q000378:metabolism; D006801:Humans; D007424:Intracellular Fluid / Q000378:metabolism; D008214:Lymphocytes / Q000378:metabolism*; D008954:Models, Biological; D009995:Osmosis; D011188:Potassium / Q000097:blood*; D012964:Sodium / Q000097:blood*
chemical_list: D012964:Sodium; D011188:Potassium