title: Transcellular transport of benzoic acid across Caco-2 cells by a pH-dependent and carrier-mediated transport mechanism.
abstract: The pH-dependent transcellular transport of [14C]benzoic acid across a Caco-2 cell monolayer is shown to be mediated by a monocarboxylic acid-specific carrier-mediated transport system, localized on the apical membrane. Evidence for the carrier-mediated transport of benzoic acid includes (a) the significant temperature and concentration dependence, (b) the metabolic energy dependence, (c) the inhibition by unlabeled benzoic acid and other monocarboxylic acids, (d) countertransport effects on the uptake of [14C]benzoic acid, and (e) effects of a proteinase (papain) and amino acid-modifying reagents. Furthermore, since carbonylcyanide p-trifluoromethoxyphenylhydrazone and nigericin significantly inhibited the transport of [14C]benzoic acid, the direct driving force for benzoic acid transport is suggested to be the inwardly directed proton gradient. From these results, together with previous observations using intestinal brush border membrane vesicles, the pH dependence of the transcellular transport of certain organic weak acids across Caco-2 cells is considered to result mainly from a proton gradient-dependent, carrier-mediated transport mechanism, rather than passive diffusion according to the pH-partition theory.
authors.affiliation: Department of Pharmaceutics, Faculty of Pharmaceutical Sciences, Kanazawa University, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Tsuji
authors.forename: H
authors.initials: H
authors.lastname: Takanaga
authors.forename: I
authors.initials: I
authors.lastname: Tamai
authors.forename: T
authors.initials: T
authors.lastname: Terasaki
mesh_terms: D000085:Acetates / Q000378:metabolism; D019342:Acetic Acid; D000963:Antimetabolites / Q000494:pharmacology; D001565:Benzoates / Q000378:metabolism*; D019817:Benzoic Acid; D001693:Biological Transport, Active; D002264:Carboxylic Acids / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism*; D002460:Cell Line; D004734:Energy Metabolism / Q000187:drug effects; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007202:Indicators and Reagents; D007408:Intestinal Absorption; D008871:Microvilli / Q000378:metabolism; D009525:Niacin / Q000378:metabolism; D010206:Papain / Q000494:pharmacology
chemical_list: D000085:Acetates; D000963:Antimetabolites; D001565:Benzoates; D002264:Carboxylic Acids; D002352:Carrier Proteins; D007202:Indicators and Reagents; D009525:Niacin; D019817:Benzoic Acid; D010206:Papain; D019342:Acetic Acid