Influence of extracellular Ca2+ on endogenous Cl- channels in Xenopus oocytes

Pflugers Arch. 1995 Apr;429(6):820-4. doi: 10.1007/BF00374806.


Removal of Ca2+ from the external bath solution evoked marked depolarization and large currents (up to several microamperes) in voltage-clamped defolliculated oocytes of Xenopus laevis. The resulting current was not carried by a cation influx but was due to a huge Cl- efflux, which could be strongly inhibited by the Cl- channel blockers flufenamic acid and niflumic acid. Removal of Mg2+ or Ba2+ from the solutions had the same effects as removing Ca2+. The reversal potential of -12 mV also indicated that Cl- channels were responsible for the large currents. Patch-clamp studies revealed a single-channel slope conductance of 90 pS. During oocyte maturation these channels remained active. The half-maximal Ca2+ concentration of about 20 microM showed that quite low doses of extracellular Ca2+ profoundly influence the electrical properties of the oocyte membrane.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Barium / pharmacology
  • Calcium / pharmacology*
  • Chloride Channels / antagonists & inhibitors
  • Chloride Channels / drug effects
  • Chloride Channels / physiology*
  • Egtazic Acid / pharmacology
  • Electric Conductivity
  • Female
  • Flufenamic Acid / pharmacology
  • Magnesium / pharmacology
  • Membrane Potentials
  • Niflumic Acid / pharmacology
  • Oocytes / physiology*
  • Patch-Clamp Techniques
  • Potassium / pharmacology
  • Xenopus laevis


  • Chloride Channels
  • Barium
  • Niflumic Acid
  • Egtazic Acid
  • Flufenamic Acid
  • Magnesium
  • Potassium
  • Calcium