title: Luminal Na+ entry into Necturus proximal tubule cells.
abstract: The dependence of intracellular Na+ activity on the electrical driving force across the luminal membrane and the presence of Cl- in the luminal perfusate was studied in Necturus proximal tubule. Intracellular Na+ and K+ activities were measured with microelectrodes filled with liquid ion exchanger. Perfusion of the tubule lumen with a NaCl-free solution caused cell Na+ activity to fall from the control value of 29.7 to 6.6 mM. In the absence of luminal driving force across the luminal membrane in accordance with simple diffusion of Na+ across this membrane. When the tubule lumen contained Na+ and Cl-, an electrically neutral component of Na+ entry into cells from the lumen appeared in addition to the diffusional component of Na+ entry.
mesh_terms: D000818:Animals; D001693:Biological Transport, Active; D066298:In Vitro Techniques; D007687:Kidney Tubules, Proximal / Q000378:metabolism*; D008433:Mathematics; D008839:Microelectrodes; D010477:Perfusion; D011188:Potassium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism*; D014562:Caudata / Q000378:metabolism*
chemical_list: D012964:Sodium; D011188:Potassium