title: Rectification of whole cell cystic fibrosis transmembrane conductance regulator chloride current.
abstract: Whole cell epithelial cystic fibrosis transmembrane conductance regulator (CFTR) Cl- currents exhibited a linear current-voltage (I-V) relationship with high symmetrical transmembrane Cl- concentrations. However, when intracellular Cl- (Cli-) was reduced by replacement with glutamate, I-V relationships were outwardly rectifying. Rectification was not affected by reducing extracellular Cl- to eliminate or reverse the gradient, indicating that rectification is not a function of the Cl- gradient. Rectification was affected by Cli- in a concentration-dependent manner, and it was weaker when Cli- was reduced by replacement with sucrose. These characteristics are identical to those of the cardiac isoform of CFTR, and the experimental data could be simulated by an Eyring rate theory model assuming that permeating anions interact at a single binding site within the channel pore. No evidence was found for multiple binding sites. These results indicate that rectification is a function of the concentration and permeability of the anions inside the cell. It is concluded that rectification of CFTR Cl- current is a property of ion channel permeation that would occur under physiological conditions and that permeation of the epithelial and cardiac isoforms of CFTR is identical.
authors.affiliation: Department of Physiology, Case Western Reserve University, Cleveland, Ohio 44106.
authors.forename: J L
authors.initials: JL
authors.lastname: Overholt
authors.forename: A
authors.initials: A
authors.lastname: Saulino
authors.forename: M L
authors.initials: ML
authors.lastname: Drumm
authors.forename: R D
authors.initials: RD
authors.lastname: Harvey
mesh_terms: D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D000838:Anions; D002460:Cell Line; D018118:Chloride Channels / Q000502:physiology*; D002712:Chlorides / Q000494:pharmacology; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D004553:Electric Conductivity; D004848:Epithelium / Q000502:physiology; D006168:Guinea Pigs; D006321:Heart / Q000502:physiology; D008565:Membrane Proteins / Q000235:genetics / Q000502:physiology*; D010766:Phosphorylation; D014162:Transfection
chemical_list: D000838:Anions; D018118:Chloride Channels; D002712:Chlorides; D008565:Membrane Proteins; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D005576:Colforsin; D000255:Adenosine Triphosphate; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D015056:1-Methyl-3-isobutylxanthine