The epithelial calcium channel, ECaC, is activated by hyperpolarization and regulated by cytosolic calcium

Biochem Biophys Res Commun. 1999 Aug 2;261(2):488-92. doi: 10.1006/bbrc.1999.1059.


The recently cloned epithelial Ca(2+) channel, ECaC, which is expressed in the apical membrane of 1,25-dihydroxyvitamin D(3)-responsible epithelia, was characterized in Xenopus laevis oocytes by measuring the Ca(2+)-activated Cl(-) current which is a sensitive read-out of the Ca(2+) influx. ECaC-expressing oocytes responded to a voltage ramp with a maximal inward current of -2.1 +/- 0.3 microA at a holding potential of -99 +/- 1 mV. The inward current decreased progressively at less negative potentials and at +50 mV a small Ca(2+)-induced outward current was observed. The Ca(2+) influx-evoked current at a hyperpolarizing pulse to -100 mV displayed a fast activation followed by a rapid but partial inactivation. Loading of the oocytes with the Ca(2+) chelator BAPTA delayed the activation and blocked the inactivation of ECaC. When a series of brief hyperpolarizing pulses were given a significant decline in the peak response and subsequent plateau phase was observed. In conclusion, the distinct electrophysiological features of ECaC are hyperpolarization-dependent activation, Ca(2+)-dependent regulation of channel conductance and desensitization during repetitive stimulation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Calcium / metabolism*
  • Calcium Channels / drug effects
  • Calcium Channels / genetics
  • Calcium Channels / metabolism*
  • Chelating Agents / pharmacology
  • Cytosol / metabolism
  • Egtazic Acid / analogs & derivatives
  • Egtazic Acid / pharmacology
  • Female
  • In Vitro Techniques
  • Membrane Potentials
  • Oocytes / drug effects
  • Oocytes / metabolism
  • Rabbits
  • TRPV Cation Channels
  • Xenopus laevis


  • Calcium Channels
  • Chelating Agents
  • ECaC protein, Oryctolagus cuniculus
  • TRPV Cation Channels
  • Egtazic Acid
  • 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid
  • Calcium