Bending the primary cilium opens Ca2+-sensitive intermediate-conductance K+ channels in MDCK cells

J Membr Biol. 2003 Feb 1;191(3):193-200. doi: 10.1007/s00232-002-1055-z.


Increasing tubular fluid flow rate has previously been shown to induce K+ secretion in mammalian cortical collecting duct. The mechanism responsible was examined in the present study using MDCK cells as a model. The change in membrane potential difference (EM) of MDCK cells was measured with a fluorescent voltage-sensitive dye, DiBAC4(3), when the cell's primary cilium was continuously bent with a micropipette or by the flow of perfusate. Bending the cilium produced a hyperpolarization of the membrane that lagged behind the increase in intracellular Ca2+ concentration by an average of 36 seconds. Gd3+, an inhibitor of the flow-induced Ca2+ increase, prevented the hyperpolarization. Blocking K+ channels with Ba2+ reduced the flow-induced hyperpolarization, implying that it resulted from activation of Ca2+-sensitive K+ channels. Further studies demonstrated that the hyperpolarization was diminished by the blocker of Ca2+-activated K+ channels, charybdotoxin, whereas iberiotoxin or apamin had no effect, results consistent with the activation of intermediate-conductance Ca2+-sensitive K+ channels. RT-PCR analysis and sequencing confirmed the presence of intermediate-conductance K+ channels in MDCK cells. We conclude that the increase in intracellular Ca2+ associated with bending of the primary cilium is the cause of the hyperpolarization and increased K+ conductance in MDCK cells.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Cell Line
  • Cilia / drug effects
  • Cilia / physiology*
  • Cilia / ultrastructure
  • Dogs
  • Electric Conductivity
  • Gadolinium / pharmacology
  • Ion Channel Gating / drug effects
  • Ion Channel Gating / physiology*
  • Kidney / physiology*
  • Kidney / ultrastructure
  • Mechanotransduction, Cellular / physiology*
  • Membrane Potentials / drug effects
  • Membrane Potentials / physiology
  • Motion
  • Physical Stimulation / methods
  • Potassium / physiology
  • Potassium Channels, Calcium-Activated / drug effects
  • Potassium Channels, Calcium-Activated / physiology*


  • Potassium Channels, Calcium-Activated
  • Gadolinium
  • Potassium