Apical membrane chloride channels in a colonic cell line activated by secretory agonists

D. R. Halm, G. R. Rechkemmer, Robert Schoumacher, R. A. Frizzell

Research output: Contribution to journalArticle

100 Citations (Scopus)

Abstract

We characterized the anion channel responsible for the increase in apical membrane Cl secretion using a model salt-secreting epithelium, the T84 colonic cell line. The adenosine 3',5'-cyclic monophosphate (cAMP)-mediated secretagogues, prostaglandin E2, forskolin, and 8-bromo-cAMP, evoked activity of an outwardly rectifying Cl channel in previously quiet cell-attached membrane patches. The channel remained active in excised, inside-out membranes, where its single-channel conductance was 40-45 pS at 0 mV with 160 mM NaCl in pipette and bath. Selectivities were P(Cl)/P(Na) = 50 and for halides I(1.8)/Br(1.4)/Cl(1.0)/F(0.4). This halide sequence illustrates that the ability of various anions to undergo transepithelial secretion is determined by the selectivity of the basolateral membrane Cl entry step rather than by the apical Cl channel. Open-channel probability increased with depolarization, an effect that would adjust the rate of Cl exit across secretory cell apical membranes with agonist-induced changes in apical membrane potential. Comparison with the properties of Cl channels detected in other cell types suggests that this cAMP-stimulated Cl channel is uniquely present in the apical membranes of salt-secreting epithelial cells.

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Cell Physiology
Volume254
Issue number4
StatePublished - Jan 1 1988

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Chloride Channels
Ion Channels
Cells
Membranes
Cell Line
Anions
Cell membranes
Salts
Cell Membrane
8-Bromo Cyclic Adenosine Monophosphate
Colforsin
Baths
Dinoprostone
Cyclic AMP
Membrane Potentials
Depolarization
Epithelium
Epithelial Cells

All Science Journal Classification (ASJC) codes

  • Physiology
  • Cell Biology

Cite this

Apical membrane chloride channels in a colonic cell line activated by secretory agonists. / Halm, D. R.; Rechkemmer, G. R.; Schoumacher, Robert; Frizzell, R. A.

In: American Journal of Physiology - Cell Physiology, Vol. 254, No. 4, 01.01.1988.

Research output: Contribution to journalArticle

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AB - We characterized the anion channel responsible for the increase in apical membrane Cl secretion using a model salt-secreting epithelium, the T84 colonic cell line. The adenosine 3',5'-cyclic monophosphate (cAMP)-mediated secretagogues, prostaglandin E2, forskolin, and 8-bromo-cAMP, evoked activity of an outwardly rectifying Cl channel in previously quiet cell-attached membrane patches. The channel remained active in excised, inside-out membranes, where its single-channel conductance was 40-45 pS at 0 mV with 160 mM NaCl in pipette and bath. Selectivities were P(Cl)/P(Na) = 50 and for halides I(1.8)/Br(1.4)/Cl(1.0)/F(0.4). This halide sequence illustrates that the ability of various anions to undergo transepithelial secretion is determined by the selectivity of the basolateral membrane Cl entry step rather than by the apical Cl channel. Open-channel probability increased with depolarization, an effect that would adjust the rate of Cl exit across secretory cell apical membranes with agonist-induced changes in apical membrane potential. Comparison with the properties of Cl channels detected in other cell types suggests that this cAMP-stimulated Cl channel is uniquely present in the apical membranes of salt-secreting epithelial cells.

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