title: Transepithelial transport of fluorescein in Caco-2 cell monolayers and use of such transport in in vitro evaluation of phenolic acid availability.
abstract: Fluorescein is a marker-dye customary applied to the evaluation of tight-junctional permeability of epithelial cell monolayers. However, the true mechanism for the permeation has not been elucidated. Transepithelial transport of fluorescein in Caco-2 cell monolayers was therefore examined. Fluorescein transport was dependent on pH, and in a vectorical way in the apical-basolateral direction, but it was independent of the tight-junctional permeability of monolayers of these human intestinal cells. The permeation of fluorescein was concentration-dependent and saturable; the Michaelis constant was 7.7 mM and the maximum velocity was 40.3 nmol min(-1) (mg protein)(-1). Benzoic acid competitively inhibited fluorescein transport, suggesting that fluorescein is transported by a monocarboxylic acid transporter (MCT). Antioxidative polyphenolic compounds such as ferulic acid from dietary sources, competitively inhibited the permeation of fluorescein. These compounds probably share a transport carrier with fluorescein. Measurement of the effects of phenolic acids on fluorescein transport across Caco-2 monolayers would be a useful way to evaluate the intestinal absorption or bioavailability of dietary phenolic acids.
authors.affiliation: Applied Bioresearch Center, Research & Development Dept., Kirin Brewery Co., Ltd., 3 Miyaharacho, Takasaki-shi, Gunma 370-1295, Japan. konishiy@kirin.co.jp
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Konishi
authors.forename: Keiko
authors.initials: K
authors.lastname: Hagiwara
authors.forename: Makoto
authors.initials: M
authors.lastname: Shimizu
mesh_terms: D019817:Benzoic Acid / Q000494:pharmacology; D001682:Biological Availability; D018938:Caco-2 Cells; D003373:Coumaric Acids / Q000494:pharmacology; D004347:Drug Interactions; D017097:Electric Impedance; D004847:Epithelial Cells / Q000378:metabolism; D019793:Fluorescein / Q000493:pharmacokinetics*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D062385:Hydroxybenzoates / Q000493:pharmacokinetics*; D007408:Intestinal Absorption / Q000187:drug effects; D007413:Intestinal Mucosa / Q000166:cytology / Q000378:metabolism*; D007546:Isoquinolines / Q000378:metabolism; D027501:Monocarboxylic Acid Transporters / Q000378:metabolism*; D019108:Tight Junctions / Q000187:drug effects / Q000502:physiology
chemical_list: D003373:Coumaric Acids; D062385:Hydroxybenzoates; D007546:Isoquinolines; D027501:Monocarboxylic Acid Transporters; D019817:Benzoic Acid; C017475:lucifer yellow; C004999:ferulic acid; C017616:phenolic acid; D019793:Fluorescein