title: The mechanism of electrodiffusive K+ transport in leaky epithelia and some of its consequences for anion transport.
abstract: The ventricular membrane of the epithelium from the choroid plexus of Necturus maculosus was probed with double-barrelled ion-selective microelectrodes while the ventricular bathing solution was changed abruptly. The transient states induced by increasing the external concentration of K+ or by the application of ouabain showed that the passive movements of K+ across the ventricular membrane were electro-diffusive and could be described by the Goldmann equation and one constant permeability (PK) of 24 X 10(-6) cm s-1. The passive efflux was balanced by a ouabain-sensitive influx. PK was different in different steady states; when the cell was acidified by half a pH unit by increasing CO2 in the bathing solutions from 1 to 5%, then PK decreased to 13 X 10(-6) cm s-1. Removal of Cl- from the bathing solution increased PK by 50% and reduction of Cl- transport by furosemide did not alter PK, consequently major movements of K+ were independent of Cl- movements. Depolarizations of the cell caused an increase in the cellular HCO-3 concentration due to an electrodiffusive permeability (PHCO3), the value of which was estimated to 17 X 10(-6) cm s-1.
mesh_terms: D000818:Animals; D000838:Anions / Q000378:metabolism*; D001693:Biological Transport, Active; D002712:Chlorides / Q000378:metabolism; D004058:Diffusion; D004563:Electrochemistry; D004848:Epithelium / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D009337:Necturus; D010042:Ouabain / Q000494:pharmacology; D010539:Permeability; D011188:Potassium / Q000378:metabolism*
chemical_list: D000838:Anions; D002712:Chlorides; D010042:Ouabain; D011188:Potassium