Document Detail

GTP-binding proteins regulate high conductance anion channels in rat bile duct epithelial cells.
MedLine Citation:
PMID:  7687295     Owner:  NLM     Status:  MEDLINE    
Epithelial cells from the intrahepatic bile duct contribute to bile formation, but little is known of the cellular mechanisms responsible. In these studies, we have characterized the endogenous GTP-binding proteins (G proteins) present in these cells and evaluated their role in regulation of high conductance anion channels. G proteins were identified in purified plasma membranes of isolated bile duct epithelial cells using specific antisera on Western blots, and ion channel activity was measured in excised inside-out membrane patches using patch-clamp recording techniques. In patches without spontaneous channel activity, addition of cholera toxin to the cytoplasmic surface had no effect (n = 10). Addition of pertussis toxin caused an activation of channels in 13/34 (38%) attempts, as detected by an increase in channel open probability. Activated channels were anion selective (gluconate/Cl- permeability ratio of 0.17 +/- 0.04) and had a unitary conductance of approximately 380 pS. Channel open probability was also increased by the nonhydrolyzable GDP analogue guanosine 5'-0-(2-thiodiphosphate) in 8/14 (57%) attempts. In contrast, channel open probability was rapidly and reversibly decreased by the nonhydrolyzable analogue of GTP 5' guanylylimidodiphosphate in 7/9 (78%) attempts. Western blotting with specific antisera revealed that both Gi alpha-2 and Gi alpha-3 were present in significant amounts, whereas Gi alpha-1 and Go alpha were not detected. These studies indicate that in bile duct epithelial cells, high conductance anion channels are inhibited, in a membrane-delimited manner, by PTX-sensitive G proteins.
J M McGill; T W Gettys; S Basavappa; J G Fitz
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  The Journal of membrane biology     Volume:  133     ISSN:  0022-2631     ISO Abbreviation:  J. Membr. Biol.     Publication Date:  1993 May 
Date Detail:
Created Date:  1993-08-19     Completed Date:  1993-08-19     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  0211301     Medline TA:  J Membr Biol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  253-61     Citation Subset:  IM    
Duke University Medical Center, Department of Medicine, Durham, North Carolina 27710.
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MeSH Terms
Anions / metabolism*
Bicarbonates / metabolism,  pharmacokinetics
Bile Ducts, Intrahepatic / chemistry,  cytology,  physiology*
Biological Transport / drug effects,  physiology
Blotting, Western
Cell Membrane / chemistry,  physiology,  ultrastructure
Cells, Cultured
Chlorides / metabolism,  pharmacokinetics
Epithelial Cells
Epithelium / chemistry,  physiology
GTP-Binding Proteins / analysis,  physiology*
Ion Channels / physiology*
Membrane Potentials / physiology
Pertussis Toxin
Rats, Sprague-Dawley
Virulence Factors, Bordetella / pharmacology
Grant Support
Reg. No./Substance:
0/Anions; 0/Bicarbonates; 0/Chlorides; 0/Ion Channels; 0/Virulence Factors, Bordetella; EC Toxin; EC 3.6.1.-/GTP-Binding Proteins

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