Pflügers Archiv

, Volume 431, Issue 1, pp 52–65 | Cite as

Maxi K+ channels in the basolateral membrane of the exocrine frog skin gland regulated by intracellular calcium and pH

  • Henning K. Andersen
  • Valerie Urbach
  • Emmy Van Kerkhove
  • Ena Prosser
  • Brian J. Harvey
Original Article Transport Processes, Metabolism and Endocrinology; Kidney, Gastrointestinal Tract and Exorcrine Glands


With the single-channel patch-clamp technique we have identified Ca2+-sensitive, high-conductance (maxi) K+ channels in the basolateral membrane (BLM) of exocrine gland cells in frog skin. Under resting conditions, maxi K+ channels were normally quiescent, but they were activated by muscarinic agonists or by high serosal K+. In excised inside-out patches and with symmetrical 140 mmol/l K+, single-channel conductance was 200 pS and the channel exhibited a high selectivity for K+ over Na+. Depolarization of the BLM increased maxi K+ channel activity. Increasing cytosolic free Ca2+ (by addition of 100 nmol/l thapsigargin to the bathing solution of cell-attached patches also increased channel activity, whereas thapsigargin had no effect when added to excised inside-out patches. An increase in cytosolic free Ca2+ directly activated channel activity in a voltage-dependent manner. Maxi K+ channel activity was sensitive to changes in intracellular pH, with maximal activity at pH 7.4 and decreasing activities following acidification and alkalinization. Maxi K+ channel outward current was reversibly blocked by micromolar concentrations of Ba2+ from the cytosolic and extracellular site, and was irreversibly blocked by micromolar concentrations of charybdotoxin and kaliotoxin from the extracellular site in outside-out patches.

Key words

Calcium Frog skin glands Maxi K+ channel Patch clamp pH Thapsigargin 


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Copyright information

© Springer-Verlag 1995

Authors and Affiliations

  • Henning K. Andersen
    • 1
  • Valerie Urbach
    • 2
  • Emmy Van Kerkhove
    • 3
  • Ena Prosser
    • 2
  • Brian J. Harvey
    • 2
  1. 1.Zoophysiological LaboratoryAugust Krogh InstituteCopenhagen ØDenmark
  2. 2.Cellular Physiology Research Unit, CPRU, Department of PhysiologyUniversity College CorkCorkIreland
  3. 3.LUC, Dept. MBW-FysiologieLimburgs Universitair CentrumDiepenbechBelgium

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