title: Uptake of aristolochic acid I into Caco-2 cells by monocarboxylic acid transporters.
abstract: The uptake mechanism of aristolochic acid I (AAI) was investigated using Caco-2 cells cultured on dishes and permeable membranes. The uptake of AAI from the apical membrane of Caco-2 cells cultured on a dish was rapid, and a decrease in the pH of the incubation medium significantly increased uptake. Incubation at low temperature (4°C) and treatment with sodium azide (a metabolic inhibitor) or carbonylcyanide p-trifluoromethoxyphenylhydrazone (a protonophore) significantly inhibited the AAI uptake. Coincubation with L-lactic acid or benzoic acid, typical substrates for the proton-linked monocarboxylic acid transporters (MCTs), significantly decreased the AAI uptake, as did coincubation with α-cyano-4-hydroxycinnamate (an inhibitor of MCTs). Dixon plotting revealed the competitive inhibition of benzoic acid on the AAI uptake. To confirm the AAI uptake via MCTs, the apical-to-basolateral transport of AAI was investigated using the Caco-2 cells cultured on the permeable membranes. The transport of AAI at pH 6.0 was markedly higher than that at pH 7.4, and was significantly decreased by coincubation with benzoic acid. These results suggest that the uptake of AAI from the apical membrane of Caco-2 cells is mediated mainly by MCTs along with benzoic acid.
authors.affiliation: School of Pharmaceutical Sciences, Health Sciences University of Hokkaido.
authors.forename: Osamu
authors.initials: O
authors.lastname: Kimura
authors.forename: Koichi
authors.initials: K
authors.lastname: Haraguchi
authors.forename: Chiho
authors.initials: C
authors.lastname: Ohta
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Koga
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Kato
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Endo
mesh_terms: D034341:Aristolochic Acids / Q000494:pharmacology*; D019817:Benzoic Acid / Q000378:metabolism; D018938:Caco-2 Cells; D006801:Humans; D006863:Hydrogen-Ion Concentration; D027501:Monocarboxylic Acid Transporters / Q000378:metabolism*; D013696:Temperature
chemical_list: D034341:Aristolochic Acids; D027501:Monocarboxylic Acid Transporters; D019817:Benzoic Acid; C000228:aristolochic acid I