Pflügers Archiv

, Volume 444, Issue 1, pp 167–177

Regulation of cloned, Ca2+-activated K+ channels by cell volume changes

  • Morten Grunnet
  • Nanna MacAulay
  • Nanna K. Jorgensen
  • Bo Jensen
  • Søren-Peter Olesen
  • Dan A. Klaerke
Original Article

DOI: 10.1007/s00424-002-0782-4

Cite this article as:
Grunnet, M., MacAulay, N., Jorgensen, N.K. et al. Pflügers Arch - Eur J Physiol (2002) 444: 167. doi:10.1007/s00424-002-0782-4

Abstract.

Ca2+-activated K+ channels of big (hBK), intermediate (hIK) or small (rSK3) conductance were co-expressed with aquaporin 1 (AQP1) in Xenopus laevis oocytes. hBK channels were activated by depolarization, whereas hIK and rSK3 channels were activated by direct injection of Ca2+ or Cd2+ into the oocyte cytoplasm, before the oocytes were subjected to hyperosmolar or hypoosmolar (±50 mOsm mannitol) challenges. In all cases, the oocytes responded rapidly to the osmotic changes with shrinkage or swelling and the effects on the K+ currents were measured. hIK and rSK3 currents were highly sensitive to volume changes and increased immediately to 178% (hIK) or 165% (rSK3) of control in response to swelling and decreased to 64% (hIK) or 61% (rSK3) of control after shrinkage. These responses were dependent on the channels being pre-activated and were almost totally abolished after injection of cytochalasin D into the oocyte cytoplasm (final concentration: 1 µM). In contrast, hBK channels showed only a minor sensitivity to volume changes; the hBK channel activity decreased approximately 20% after swelling and increased approximately 20% after shrinkage. The opposite effects of volume changes on hIK/rSK3 and hBK channels suggest that the significant stimulation of hIK and rSK3 channels during swelling is not mediated by changes in intracellular Ca2+, but rather through interactions with the cytoskeleton, provided that a sufficient basal concentration of intracellular Ca2+ or Cd2+ is present.

Volume regulation Cytoskeleton Ca2+-activated K+ channels hBK channels hIK channels rSK3 channels Aquaporin 1 Co-expression

Copyright information

© Springer-Verlag 2002

Authors and Affiliations

  • Morten Grunnet
    • 1
  • Nanna MacAulay
    • 1
  • Nanna K. Jorgensen
    • 1
  • Bo Jensen
    • 1
  • Søren-Peter Olesen
    • 1
  • Dan A. Klaerke
    • 1
  1. 1.Department of Medical Physiology, The Panum Institute, University of Copenhagen, Blegdamsvej 3, 2200 Copenhagen N, DenmarkDenmark