Properties of single- and double-barreled Cl channels of shark rectal gland in planar bilayers

Steven C. Sansom, Sandra L. Carosi

Research output: Contribution to journalArticle

4 Scopus citations

Abstract

Chloride channels from the apical plasma membrane fraction of rectal gland of Squalus acanthias were characterized by incorporation into planar bilayers in the presence of cAMPPK/ATP. In a total of 80 bilayer preparations, 21 Cl-selective channels were observed as single channels and 13 as pairs. This was a significantly greater number of double Cl channels than expected from a binomial distribution. The double Cl channels were divided into two groups based on kinetic and voltage-dependent behavior. One group had properties identical to the single channels (gb1) while the other was consistent with a doublebarreled channel (gb2) with coordinated activity between protochannels. The single-channel slope conductances of gb1 and gb2 from -60 to +20 mV with a 250/70 m m KCl gradient were 41 and 75 pS, respectively. With symmetrical 250 m m KCl, the I-V relation of gb1 showed outward rectification with 47.8 ± 6.6 pS at cis negative potentials and 68.9±6.1 pS at cis positive potentials. gb1 was open from 70 to 95% at all electrochemical potentials from -80 to +40 mV. gb2 was steeply voltage dependent between -80 and -20 mV. Both gb1 and gb2 were insensitive to Ca (from 100 n m to 1 μm), blocked by 0.1 m m DIDS and highy selective for chloride. These data suggest that double-barreled Cl channels are related to the family of small, outwardly rectifying Cl channels of epithelial membranes.

Original languageEnglish (US)
Pages (from-to)67-73
Number of pages7
JournalThe Journal of Membrane Biology
Volume126
Issue number1
DOIs
StatePublished - Feb 1992

Keywords

  • Cl channels
  • anion selectivity
  • apical membrane
  • planar lipid bilayers
  • shark rectal gland

ASJC Scopus subject areas

  • Biophysics
  • Physiology
  • Cell Biology

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