Pflügers Archiv

, Volume 422, Issue 6, pp 546–551 | Cite as

K+ recirculation in A6 cells at increased Na+ transport rates

  • M. Granitzer
  • W. Nagel
  • J. Crabbé
Transport Processes, Metabolism and Endocrinology; Kidney, Gastrointestinal Tract, and Exocrine Glands


Homocellular regulation of K+ at increased transcellular Na+ transport implies an increase in K+ exit to match the intracellular K+ load. Increased K+ conductance, gK, was suggested to account for this gain. We tested whether such a mechanism is operational in A6 monolayers. Na+ transport was increased from 5.1±1.0 μA/cm2 to 20.7±1.3 μA/cm2 by preincubation with 0.1 μmol/l dexamethasone for 24 h. Basolateral K+ conductances were derived from transference numbers of K+, tK, and basolateral membrane conductances, gb, using conventional microelectrodes and circuit analysis with application of amiloride. Activation of Na+ transport induced an increase in gb from 0.333±0.067 mS/ cm2 to 1.160±0.196 mS/cm2 and tK was reduced to 0.22±0.01 from a value of 0.70±0.05 in untreated control tissues. As a result, gK remained virtually unchanged at increased Na+ transport rates. The increase in gb after dexamethasone was due to activation of a conductive leak pathway presumably for Cl. Increased K+ efflux, IK, was a consequence of the larger driving force for K+ exit due to depolarization at an elevated Na+ transport rate. The relationship between calculated K+ fluxes and Na+ transport rate, measured as the Isc, is described by the linear function IK=0.624×INa−0.079, which conforms with a stoichiometry 2∶3 for the fluxes of K+ and Na+ in the Na+/K+-ATPase pathway. Our data show that homocellular regulation of K+ in A6 cells is not due to up-regulation of g K .

Key words

Microelectrodes Basolateral K+ conductance K+ currents Homocellular regulation 


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Copyright information

© Springer-Verlag 1993

Authors and Affiliations

  • M. Granitzer
    • 1
  • W. Nagel
    • 1
  • J. Crabbé
    • 1
  1. 1.Département de PhysiologieUniversité Catholique de Louvain, Tour Harvey ENDO 5530BruxellesBelgium

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