title: Sodium/proton exchange in mouse neuroblastoma cells.
abstract: The sudden addition of Na+ to mouse neuroblastoma cells suspended in Na+-free medium causes a rapid but transient increase in the rate of H+ release from the cells. Li+ can substitute for Na+, but addition of choline, K+, or Ca2+ has no effect. This process has the following properties: it is distinct from metabolic acid production, it does not require ATP, and it saturates at about 40 mM external Na+; it is independent of membrane potential and can be mimicked by addition of the Na+/H+ ionophore monensin to cells in Na+-containing media. In contrast, a net uptake of protons is observed when Na+-loaded cells are suddenly exposed to Na+-free medium. Na+-induced H+ extrusion is accompanied by a rise in intracellular pH, as inferred from an enhanced net uptake of weak acids and from direct pH measurements on lysed cells. Conversely, Na+ uptake by the cells is stimulated upon lowering the intracellular pH with externally applied acetate. Na+-dependent proton transport, intracellular alkalinization, and acetate-stimulated Na+ uptake are completely inhibited by the diuretic amiloride (0.2 mM) and do not occur in digitonin-permeabilized cells. It is concluded that the plasma membrane of neuroblastoma cells contains an electroneutral Na+/H+ exchange system which is involved in the regulation of intracellular pH.
mesh_terms: D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D000838:Anions; D001693:Biological Transport, Active / Q000187:drug effects; D002460:Cell Line; D006863:Hydrogen-Ion Concentration; D007474:Ion Exchange; D007773:Lactates / Q000378:metabolism; D019344:Lactic Acid; D051379:Mice; D008985:Monensin / Q000494:pharmacology; D009447:Neuroblastoma / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D000838:Anions; D007773:Lactates; D019344:Lactic Acid; D000584:Amiloride; D008985:Monensin; D012964:Sodium