title: Functional characterization of monocarboxylic acid, large neutral amino acid, bile acid and peptide transporters, and P-glycoprotein in MDCK and Caco-2 cells.
abstract: Bidirectional transport studies were conducted to determine whether substrates of five intestinal transporters showed carrier-mediated asymmetric transport across MDCK (Madin-Darby canine kidney) cell monolayers grown under standard conditions. Drug concentrations were quantitated using liquid scintillation counting, liquid chromatography/mass spectrometry/mass spectrometry, or liquid chromatography/mass spectrometry. In the presence of a pH gradient, benzoic acid exhibited net apical-to-basolateral transport, with apparent permeability ratios (apical-to-basolateral permeability/basolateral-to-apical permeability) ranging from 14 to 25. The addition of valproic acid reduced the permeability ratio by 70-90%. Cephalexin transport also exhibited net absorption in the presence of a pH gradient, with apparent permeability ratios ranging from 14 to 71, depending on growth conditions. Radiolabeled phenylalanine exhibited a low level of carrier-mediated absorption with an apparent permeability ratio of 1.8 that was reduced to 1.0 in the presence of unlabeled L-phenylalanine. Taurocholic acid did not exhibit carrier-mediated absorption. Cyclosporine and fexofenadine exhibited P-glycoprotein-mediated efflux from both MDCK and Caco-2 cells, which was more sensitive to inhibition in MDCK cells. These results suggest that although MDCK cell monolayers may be a useful model for evaluating transport by the absorptive monocarboxylic acid and peptide transporters and the efflux transporter, P-glycoprotein, they are not useful for predicting large neutral amino acid or bile acid transport in the intestine.
authors.affiliation: Department of Biopharmaceutical Sciences, School of Pharmacy, University of California, San Francisco, 513 Parnassus Avenue, Room U-68, San Francisco, California 94143-0446, USA.
authors.forename: Wendy S
authors.initials: WS
authors.lastname: Putnam
authors.forename: Srinivasan
authors.initials: S
authors.lastname: Ramanathan
authors.forename: Lin
authors.initials: L
authors.lastname: Pan
authors.forename: Lori H
authors.initials: LH
authors.lastname: Takahashi
authors.forename: Leslie Z
authors.initials: LZ
authors.lastname: Benet
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D026921:Amino Acid Transport Systems, Neutral / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000818:Animals; D018938:Caco-2 Cells; D002352:Carrier Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002460:Cell Line; D004285:Dogs; D006801:Humans; D006913:Hydroxysteroid Dehydrogenases; D008562:Membrane Glycoproteins; D027501:Monocarboxylic Acid Transporters / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010455:Peptides / Q000493:pharmacokinetics*; D010539:Permeability; D013379:Substrate Specificity; D045002:3-alpha-Hydroxysteroid Dehydrogenase (B-Specific)
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D026921:Amino Acid Transport Systems, Neutral; D002352:Carrier Proteins; D006913:Hydroxysteroid Dehydrogenases; D008562:Membrane Glycoproteins; D027501:Monocarboxylic Acid Transporters; D010455:Peptides; C037643:bile acid binding proteins; C435496:AKR1C2 protein, human; D045002:3-alpha-Hydroxysteroid Dehydrogenase (B-Specific)