title: H+-peptide cotransport in the human bile duct epithelium cell line SK-ChA-1.
abstract: This study describes for the first time the presence of H+-peptide cotransport in cells of the bile duct. Uptake of [glycine-1-14C]glycylsarcosine ([14C]Gly-Sar) in human extrahepatic cholangiocarcinoma SK-ChA-1 cells was stimulated sevenfold by an inwardly directed H+ gradient. Transport was mediated by a low-affinity system with a transport constant (Kt) value of 1.1 mM. Several dipeptides, cefadroxil, and delta-aminolevulinic acid, but not glycine and glutathione, were strong inhibitors of Gly-Sar uptake. SK-ChA-1 cells formed tight, polarized monolayers on permeable membranes. The transepithelial electrical resistance was 856 +/- 29 omega x cm(2). The transepithelial flux of [14C]Gly-Sar in apical-to-basolateral direction exceeded the basolateral-to-apical flux 11-fold. Uptake was 20-fold higher from the apical side. RT-PCR analysis using primer pairs specific for the intestinal-type peptide transporter (PEPT1) or kidney-type (PEPT2) revealed that the transport system expressed in SK-ChA-1 and also in cells of the native rabbit bile duct is PEPT1. Immunohistochemistry localized PEPT1 to the apical membrane of cholangiocytes of mouse extrahepatic biliary duct. We conclude that the cells of the mammalian extrahepatic biliary tract epithelium express the intestinal-type H+-peptide cotransporter in their apical membrane. SK-ChA-1 cells represent a convenient model to study the physiological and clinical aspects of peptide transport in cholangiocytes.
authors.affiliation: Institute of Biochemistry, Department of Biochemistry/Biotechnology, Halle D-06120, D-85350 Germany.
authors.forename: Ilka
authors.initials: I
authors.lastname: Knütter
authors.forename: Isabel
authors.initials: I
authors.lastname: Rubio-Aliaga
authors.forename: Michael
authors.initials: M
authors.lastname: Boll
authors.forename: Gerd
authors.initials: G
authors.lastname: Hause
authors.forename: Hannelore
authors.initials: H
authors.lastname: Daniel
authors.forename: Klaus
authors.initials: K
authors.lastname: Neubert
authors.forename: Matthias
authors.initials: M
authors.lastname: Brandsch
mesh_terms: D000818:Animals; D001652:Bile Ducts / Q000166:cytology / Q000378:metabolism*; D017734:Bile Ducts, Extrahepatic / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism*; D004151:Dipeptides / Q000493:pharmacokinetics; D004847:Epithelial Cells / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D051379:Mice; D000074011:Peptide Transporter 1; D011817:Rabbits; D013379:Substrate Specificity; D027981:Symporters; D014407:Tumor Cells, Cultured
chemical_list: D002352:Carrier Proteins; D004151:Dipeptides; D000074011:Peptide Transporter 1; C082186:SLC15A1 protein, human; C489941:Slc15a1 protein, mouse; D027981:Symporters; C004194:glycylsarcosine