title: Intracellular ion activities in Necturus proximal tubule.
abstract: Ion-sensitive microelectrodes were used to measure the intracellular activities of Na, K, and Cl in proximal tubules of the perfused Necturus kidney. Cell Cl was 2-3 times higher than the value predicted for passive distribution during perfusion with normal Ringer; intracellular Na was far below the level for passive distribution. Cell Na and Cl fell to very low values when the lumen was NaCl-free. Cl entry into the tubule cell from the lumen required luminal Na. Na entered the cell across the luminal membrane both by diffusion and by coupled movement with Cl.
mesh_terms: D000818:Animals; D001692:Biological Transport; D002463:Cell Membrane Permeability; D002712:Chlorides / Q000502:physiology; D004848:Epithelium / Q000502:physiology; D007687:Kidney Tubules, Proximal / Q000502:physiology*; D008564:Membrane Potentials; D008839:Microelectrodes; D008954:Models, Biological; D011188:Potassium / Q000502:physiology; D012964:Sodium / Q000502:physiology; D014562:Caudata
chemical_list: D002712:Chlorides; D012964:Sodium; D011188:Potassium