title: Potassium secretion by cortical collecting tubule: relation to sodium absorption, luminal sodium concentration, and transepithelial voltage.
abstract: Sodium absorption and K secretion were measured in isolated perfused rabbit cortical collecting tubules. To increase the range of transport rates some tubules were dissected from rabbit pretreated with DOcA. K secretin was unaffected by varying axial volume flow from 4 to 15 nl/min. K secretion was, however, correlated with transepithelial voltage and Na absorption. The Na:K transfer ratio was 1.35. In tubules dissected from normal rabbits, K secretion was almost eliminated by reducing Na concentration in the lumen to near 0 and was unaffected by varying luminal Na concentration from 30 to 145 mM. These data, together with other experimental results reported by several investigators, are consistent with a model for K secretion that places the rate-limiting step at the Na-K pump located on the basolateral membrane. The apical (luminal) membrane appears to be highly permeable to K.
mesh_terms: D000042:Absorption; D000200:Action Potentials; D000818:Animals; D001693:Biological Transport, Active; D004305:Dose-Response Relationship, Drug; D005260:Female; D066298:In Vitro Techniques; D007684:Kidney Tubules / Q000378:metabolism*; D007685:Kidney Tubules, Collecting / Q000378:metabolism* / Q000502:physiology / Q000648:ultrastructure; D008564:Membrane Potentials; D008871:Microvilli / Q000378:metabolism; D011188:Potassium / Q000378:metabolism*; D011817:Rabbits; D012964:Sodium / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D012964:Sodium; D011188:Potassium