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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

Abstract

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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References

  1. 1.
    Filipovic D, Sackin H (1991) A calcium permeable, stretchactivated cation channel in renal proximal tubule. Am J Physiol 260:F119-F129Google Scholar
  2. 2.
    Granitzer M, Leal T, Nagel W, Crabbé J (1991) Apical and basolateral conductance in cultured A6 cells. Pflügers Arch 417:463–468Google Scholar
  3. 3.
    Granitzer M, Lyoussi B, Nagel W, Crabbé J (1991) Effect of dexamethasone on membrane conductances of cultured renal distal cells (A6). Cell Physiol Biochem 1:263–272Google Scholar
  4. 4.
    Granitzer M, Nagel W, Crabbé J (1991) Voltage dependent membrane conductances in cultured renal distal cells. Biochim Biophys Acta 1069:87–93Google Scholar
  5. 5.
    Granitzer M, Nagel W, Crabbé J (1992) Basolateral membrane conductance in A6 cells: effect of high sodium transport rate. Pflügers Arch 420:559–565Google Scholar
  6. 6.
    Hamilton KL, Benos DJ (1990) A non-selective cation channel in the apical membrane of cultured A6 kidney cells. Biochim Biophys Acta 1031:16–23Google Scholar
  7. 7.
    Higgins JT, Gebler B, Frömter E (1977) Electrical properties of amphibian urinary bladder epithelia. Pflügers Arch 371:87–97Google Scholar
  8. 8.
    Horisberger JD (1991) Apical and basolateral membrane conductances in the TBM cell line. Am J Physiol 260:C1172-C1181Google Scholar
  9. 9.
    Hunter M (1991) Potassium-selective channels in the basolateral membrane of single proximal tubule cells of frog kidney. Pflügers Arch 418:26–34Google Scholar
  10. 10.
    Hunter M, Kawahara K, Giebisch G (1986) Potassium channels along the nephron. Fed Proc 45:2723–2726Google Scholar
  11. 11.
    Illek B, Fischer H, Clauss W (1990) Aldosterone regulation of basolateral potassium channels in alveolar epithelium. Am J Physiol 259:L230-L237Google Scholar
  12. 12.
    Kawahara K, Hunter M, Giebisch G (1987) Potassium channels in Necturus proximal tubule. Am J Physiol 253: F488-F494Google Scholar
  13. 13.
    Kolb HA, Brown CDA, Murer H (1986) Characterization of a Ca-dependent maxi K channel in the apical membrane of a cultured renal epithelium (JTC-12.P3). J Membr Biol 92:207–215Google Scholar
  14. 14.
    Lang F, Rehwald W (1992) Potassium channels in renal epithelial transport regulation. Physiol Rev 72:1–32Google Scholar
  15. 15.
    Lang F, Messner G, Rehwald W (1986) Electrophysiology of sodium-coupled transport in proximal renal tubules. Am J Physiol 250:F953-F962Google Scholar
  16. 16.
    Merot J, Bidet M, Le Maout S, Tauc M, Poujeol P (1989) Two types of K+ channels in the apical membrane of rabbit proximal tubule in primary culture. Biochim Biophys Acta 978:134–144Google Scholar
  17. 17.
    Nagel W, Crabbé J (1980) Mechanism of action of aldosterone on active sodium transport across toad skin. Pflügers Arch 385:181–187Google Scholar
  18. 18.
    Nakanishi T, Balaban RS, Burg MB (1988) Survey of osmolytes in renal cell lines. Am J Physiol 255:C181-C191Google Scholar
  19. 19.
    Schultz SG (1981) Homocellular regulatory mechanisms in Na transporting epithelia: avoidance of extinction by flushthrough. Am J Physiol 241:F579-F590Google Scholar
  20. 20.
    Sugimoto T, Tanabe Y, Shigemoto R, Iwai M, Takumi T, Ohkubo H, Nakanishi S (1990) Immunohistochemical study of a rat membrane protein which induces a selective potassium permeation: its localization in the apical membrane portion of epithelial cells. J Membr Biol 113:39–47Google Scholar
  21. 21.
    Takumi T, Ohkubo H, Nakanishi S (1988) Cloning of a membrane protein that induces a slow voltage-gated potassium current. Science 242:1041–1045Google Scholar
  22. 22.
    Thomas SR, Mintz E (1987) Time-dependent apical membrane K+ and Na+ selectivity in cultured kidney cells. Am J Physiol 253:C1-C6Google Scholar

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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