title: Potassium secretion by the cortical collecting tubule.
abstract: The isolated perfused rabbit cortical collecting tubule has been shown to actively transport K from bath to lumen. The first step in this process is active uptake of K across the basolateral membrane via and Na:K exchange pump as evidenced by: 1) basolateral localization and Na:K exchange properties of the ouabain-sensitive Na,K-ATPase, 2) ouabain sensitivity of the Na and K fluxes, 3) interdependence of the Na and K fluxes, and 4) ouabain-sensitivity of 42K uptake into the cell across the basolateral membrane. At the luminal border, a significant K permeability of the apical cell membrane has been identified using electrophysiological techniques. This K permeability is insensitive to the diuretic amiloride, and, thus, differs from the pathway for Na entry, which is highly amiloride sensitive. A significant K permeability of the paracellular pathway is not apparent. It is concluded that K secretion by the rabbit cortical collecting tubule occurs via a two-step process: active uptake of K across the basolateral membrane via the Na:K exchange pump, followed by passive efflux of K across the apical membrane via an amiloride-insensitive K conductive pathway.
mesh_terms: D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D001693:Biological Transport, Active; D002463:Cell Membrane Permeability; D004848:Epithelium / Q000378:metabolism; D007473:Ion Channels / Q000378:metabolism; D007672:Kidney Cortex / Q000378:metabolism; D007684:Kidney Tubules / Q000378:metabolism*; D007685:Kidney Tubules, Collecting / Q000187:drug effects / Q000378:metabolism*; D008564:Membrane Potentials; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism*; D011817:Rabbits; D012964:Sodium / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism
chemical_list: D007473:Ion Channels; D010042:Ouabain; D000584:Amiloride; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium