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Rat and human pancreatic duct cells have small-conductance Cl- channels in their apical plasma membranes. These channels are regulated by secretin and adenosine 3',5'-cyclic monophosphate and may function in parallel with Cl(-)-HCO3- exchangers to allow HCO3- secretion from the duct cell. Using the patch-clamp technique, we have now determined the anion permeability sequence of the channel as NO3- greater than Br- approximately I- approximately Cl- much greater than HCO3- much greater than gluconate. From this we conclude 1) that anion permeation involves a weak interaction with charged sites inside the channel pore, 2) that because of the low HCO3-/Cl- permeability ratio it is unlikely that significant amounts of HCO3- could be secreted directly via the channel, and 3) that channel permeability may determine the anion selectivity of secretion. We also show that 5-nitro-2-(3-phenylpropylamino)benzoic acid blocks the small-conductance Cl- channel, whereas 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid has no effect.

Original publication

DOI

10.1152/ajpcell.1990.259.5.C752

Type

Journal article

Journal

Am J Physiol

Publication Date

11/1990

Volume

259

Pages

C752 - C761

Keywords

Animals, Anions, Bicarbonates, Chloride Channels, Copper, Electric Conductivity, Electrophysiology, Humans, Ion Channels, Membrane Potentials, Membrane Proteins, Nitrobenzoates, Pancreatic Ducts, Rats