The mechanism of electrodiffusive K+ transport in leaky epithelia and some of its consequences for anion transport |
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Authors: | T Zeuthen O Christensen J H Bærentsen M la Cour |
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Institution: | (1) The Institute of Medical Physiology A, The Panum Institute, University of Copenhagen, Blegdamsvej 3, DK-2200 Copenhagen N, Denmark |
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Abstract: | The ventricular membrane of the epithelium from the choroid plexus ofNecturus 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 (P
K) of 24×10–6 cm s–1. The passive efflux was balanced by a ouabain-sensitive influx.P
K 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%, thenP
K decreased to 13×10–6 cm s–1. Removal of Cl– from the bathing solution increasedP
K by 50% and reduction of Cl– transport by furosemide did not alterP
K, 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 (P
HCO3), the value of which was estimated to 17×10–6 cm s–1. |
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Keywords: | Microelectrodes Epithelia Choroid plexus K+ transport Electrodiffusion |
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