Characteristics of rabbit ClC-2 current expressed in Xenopus oocytes and its contribution to volume regulation

Am J Physiol. 1998 Feb;274(2):C500-12. doi: 10.1152/ajpcell.1998.274.2.C500.

Abstract

In the Xenopus oocyte heterologous expression system, the electrophysiological characteristics of rabbit ClC-2 current and its contribution to volume regulation were examined. Expressed currents on oocytes were recorded with a two-electrode voltage-clamp technique. Oocyte volume was assessed by taking pictures of oocytes with a magnification of x 40. Rabbit ClC-2 currents exhibited inward rectification and had a halide anion permeability sequence of Cl- > or = Br- >> I- > or = F-. ClC-2 currents were inhibited by 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB), diphenylamine-2-carboxylic acid (DPC), and anthracene-9-carboxylic acid (9-AC), with a potency order of NPPB > DPC = 9-AC, but were resistant to stilbene disulfonates. These characteristics are similar to those of rat ClC-2, suggesting rabbit ClC-2 as a counterpart of rat ClC-2. During a 30-min perfusion with hyposmolar solution, current amplitude at -160 mV and oocyte diameter were compared among three groups: oocytes injected with distilled water, oocytes injected with ClC-2 cRNA, and oocytes injected with ClC-2 delta NT cRNA (an open channel mutant with NH2-terminal truncation). Maximum inward current was largest in ClC-2 delta NT-injected oocytes (-5.9 +/- 0.4 microA), followed by ClC-2-injected oocytes (-4.3 +/- 0.6 microA), and smallest in water-injected oocytes (-0.2 +/- 0.2 microA), whereas the order of increase in oocyte diameter was as follows: water-injected oocytes (9.0 +/- 0.2%) > ClC-2-injected oocytes (5.3 +/- 0.5%) > ClC-2 delta NT-injected oocytes (1.1 +/- 0.2%). The findings that oocyte swelling was smallest in oocytes with the largest expressed currents suggest that ClC-2 currents expressed in Xenopus oocytes appear to act for volume regulation when exposed to a hyposmolar environment.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / pharmacology
  • 4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / pharmacology
  • Animals
  • Cell Membrane Permeability / physiology
  • Chloride Channels / drug effects
  • Chloride Channels / physiology*
  • Colforsin / pharmacology
  • Electrophysiology
  • Nerve Tissue Proteins / drug effects
  • Nerve Tissue Proteins / physiology*
  • Nitrobenzoates / pharmacology
  • Oocytes / physiology
  • Osmolar Concentration
  • Rabbits
  • Rats
  • Stilbenes / pharmacology
  • Water-Electrolyte Balance / physiology*
  • Xenopus

Substances

  • Chloride Channels
  • ClC-2 chloride channels
  • Nerve Tissue Proteins
  • Nitrobenzoates
  • Stilbenes
  • Colforsin
  • 4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid
  • 5-nitro-2-(3-phenylpropylamino)benzoic acid
  • 4,4'-dinitro-2,2'-stilbenedisulfonic acid
  • 4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid