The sodium-activated potassium channel Slack is modulated by hypercapnia and acidosis

Neuroscience. 2008 Jan 24;151(2):410-8. doi: 10.1016/j.neuroscience.2007.10.031. Epub 2007 Nov 4.


Slack (Slo 2.2), a member of the Slo potassium channel family, is activated by both voltage and cytosolic factors, such as Na(+) ([Na(+)](i)) and Cl(-) ([Cl(-)](i)). Since the Slo family is known to play a role in hypoxia, and since hypoxia/ischemia is associated with an increase in H(+) and CO(2) intracellularly, we hypothesized that the Slack channel may be affected by changes in intracellular concentrations of CO(2) and H(+). To examine this, we expressed the Slack channel in Xenopus oocytes and the Slo 2.2 protein was allowed to be inserted into the plasma membrane. Inside-out patch recordings were performed to examine the response of Slack to different CO(2) concentrations (0.038%, 5%, 12%) and to different pH levels (6.3, 6.8, 7.3, 7.8, 8.3). In the presence of low [Na(+)](i) (5 mM), the Slack channel open probability decreased when exposed to decreased pH or increased CO(2) in a dose-dependent fashion (from 0.28+/-0.03, n=3, at pH 7.3 to 0.006+/-0.005, n=3, P=0.0004, at pH 6.8; and from 0.65+/-0.17, n=3, at 0.038% CO(2) to 0.22+/-0.07, n=3, P=0.04 at 12% CO(2)). In the presence of high [Na(+)](i) (45 mM), Slack open probability increased (from 0.03+/-0.01 at 5 mM [Na(+)](i), n=3, to 0.11+/-0.01, n=3, P=0.01) even in the presence of decreased pH (6.3). Since Slack activity increases significantly when exposed to increased [Na(+)](i), even in presence of increased H(+), we propose that Slack may play an important role in pathological conditions during which there is an increase in the intracellular concentrations of both acid and Na(+), such as in ischemia/hypoxia.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Acidosis / metabolism*
  • Animals
  • Carbon Dioxide / pharmacology
  • Chlorides / pharmacology
  • Electrophysiology
  • Hydrogen-Ion Concentration
  • Hypercapnia / metabolism*
  • Nerve Tissue Proteins / physiology*
  • Oocytes / metabolism
  • Patch-Clamp Techniques
  • Plasmids / genetics
  • Potassium Channels / physiology*
  • Potassium Channels, Sodium-Activated
  • RNA, Complementary / biosynthesis
  • RNA, Complementary / genetics
  • Rats
  • Xenopus laevis


  • Chlorides
  • Nerve Tissue Proteins
  • Potassium Channels
  • Potassium Channels, Sodium-Activated
  • RNA, Complementary
  • kcnt1 protein, rat
  • Carbon Dioxide