Abstract
Using the whole cell configuration of the patch-clamp technique, we have identified an adenosine 3',5'-cyclic monophosphate (cAMP)-regulated chloride conductance in pancreatic duct cells. Basal whole cell currents in single isolated cells were very low (approximately 5 pA/pF) but could be stimulated 17-fold by elevation of intracellular cAMP. The cAMP-activated currents exhibited 1) a high chloride selectivity, 2) a near linear current-voltage relationship, 3) time and voltage independence, 4) block by 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB) but not by 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS), and 5) an anion selectivity sequence based on permeability ratios of SCN > NO3 > Br > Cl > I > HCO3 > F > ClO4 > gluconate. Currents in single cells ran down within a few minutes; however, stable chloride currents could be recorded from duct cell clusters in which four or five cells were in electrical communication. We present evidence suggesting that these cAMP-regulated currents are carried by cystic fibrosis transmembrane conductance regulator (CFTR) chloride channels. Physiologically, these CFTR channels act in parallel with chloride-bicarbonate exchangers to facilitate bicarbonate secretion across the apical plasma membrane of the duct cell.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid
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4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / analogs & derivatives
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4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / pharmacology
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Animals
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Biological Transport / drug effects
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Biological Transport / physiology
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Bromides / pharmacokinetics
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Cell Communication / physiology
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Cell Membrane / drug effects
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Cell Membrane / physiology
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Cell Membrane Permeability / physiology
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Cells, Cultured
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Chlorides / metabolism*
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Chlorides / pharmacokinetics
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Cyclic AMP / metabolism
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Cyclic AMP / physiology*
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Cystic Fibrosis Transmembrane Conductance Regulator
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Epithelial Cells
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Epithelium / metabolism
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Epithelium / physiology
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Iodine / pharmacokinetics
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Ion Channels / drug effects
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Ion Channels / physiology*
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Membrane Proteins / physiology
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Nitrates / pharmacokinetics
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Nitrobenzoates / pharmacology
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Pancreatic Ducts / cytology*
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Pancreatic Ducts / physiology*
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Pancreatic Ducts / ultrastructure
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Rats
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Rats, Wistar
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Time Factors
Substances
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Bromides
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Chlorides
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Ion Channels
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Membrane Proteins
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Nitrates
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Nitrobenzoates
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Cystic Fibrosis Transmembrane Conductance Regulator
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4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid
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5-nitro-2-(3-phenylpropylamino)benzoic acid
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Iodine
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Cyclic AMP
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4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid