Swelling-activated anion channels are essential for volume regulation of mouse thymocytes

Int J Mol Sci. 2011;12(12):9125-37. doi: 10.3390/ijms12129125. Epub 2011 Dec 8.


Channel-mediated trans-membrane chloride movement is a key process in the active cell volume regulation under osmotic stress in most cells. However, thymocytes were hypothesized to regulate their volume by activating a coupled K-Cl cotransport mechanism. Under the patch-clamp, we found that osmotic swelling activates two types of macroscopic anion conductance with different voltage-dependence and pharmacology. At the single-channel level, we identified two types of events: one corresponded to the maxi-anion channel, and the other one had characteristics of the volume-sensitive outwardly rectifying (VSOR) chloride channel of intermediate conductance. A VSOR inhibitor, phloretin, significantly suppressed both macroscopic VSOR-type conductance and single-channel activity of intermediate amplitude. The maxi-anion channel activity was largely suppressed by Gd(3+) ions but not by phloretin. Surprisingly, [(dihydroindenyl)oxy] alkanoic acid (DIOA), a known antagonist of K-Cl cotransporter, was found to significantly suppress the activity of the VSOR-type single-channel events with no effect on the maxi-anion channels at 10 μM. The regulatory volume decrease (RVD) phase of cellular response to hypotonicity was mildly suppressed by Gd(3+) ions and was completely abolished by phloretin suggesting a major impact of the VSOR chloride channel and modulatory role of the maxi-anion channel. The inhibitory effect of DIOA was also strong, and, most likely, it occurred via blocking the VSOR Cl(-) channels.

Keywords: DIOA; anion channels; phloretin; thymocytes; volume regulation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Action Potentials
  • Animals
  • Carboxylic Acids / pharmacology
  • Cell Size*
  • Chlorides / metabolism
  • Gadolinium / pharmacology
  • Indenes / pharmacology
  • Ion Channels / antagonists & inhibitors
  • Ion Channels / metabolism*
  • Mice
  • Osmotic Pressure*
  • Phloretin / pharmacology
  • Thymocytes / cytology
  • Thymocytes / metabolism*
  • Thymocytes / physiology


  • ((dihydroindenyl)oxy)alkanoic acid
  • Carboxylic Acids
  • Chlorides
  • Indenes
  • Ion Channels
  • Gadolinium
  • Phloretin