title: Comparison of bidirectional cephalexin transport across MDCK and caco-2 cell monolayers: interactions with peptide transporters.
abstract: OBJECTIVE
  Bidirectional transport studies were conducted to determine whether Madin-Darby canine kidney (MDCK) cell monolayers could be used as an alternative to the traditional Caco-2 assay as a fast-growing in vitro model of peptide transport.
  
  
  METHODS
  Transport of cephalexin and glycylsarcosine across MDCK and Caco-2 cell monolayers was quantified using LC-LC/MS. Glycylsarcosine, p-aminohippuric acid (PAH), and tetraethylammonium chloride (TEA) were tested as inhibitors of cephalexin transport.
  
  
  RESULTS
  The ratio of apparent cephalexin permeabilities (apical to basolateral/basolateral to apical) obtained from MDCK monolayers was almost 5-fold greater than that obtained from Caco-2 monolayers. The opposite trend was observed for glycylsarcosine. When MDCK monolayers were used, glycylsarcosine reduced the cephalexin/apparent permeability ratio almost 90%. PAH and TEA did not inhibit cephalexin transport across MDCK or Caco-2 cell monolayers.
  
  
  CONCLUSIONS
  MDCK cell monolayers may be a promising, fast-growing alternative to Caco-2 cells for identifying peptide transporter substrates. However, differences in the apical-to-basolateral transport of cephalexin and glycylsarcosine suggest that the basolateral transport mechanisms for these compounds are different in the two cell lines. Additionally, because the activity of the peptide transporter in MDCK cells was low, scaling factors may be required when using this cell line to predict in vivo drug absorption.
authors.affiliation: Department of Biopharmaceutical Sciences, School of Pharmacy, University of California, San Francisco 94143-0446, USA.
authors.forename: Wendy S
authors.initials: WS
authors.lastname: Putnam
authors.forename: Lin
authors.initials: L
authors.lastname: Pan
authors.forename: Ken
authors.initials: K
authors.lastname: Tsutsui
authors.forename: Lori
authors.initials: L
authors.lastname: Takahashi
authors.forename: Leslie Z
authors.initials: LZ
authors.lastname: Benet
mesh_terms: D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D018938:Caco-2 Cells; D002460:Cell Line; D002463:Cell Membrane Permeability; D002506:Cephalexin / Q000493:pharmacokinetics*; D004151:Dipeptides / Q000494:pharmacology; D004285:Dogs; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007668:Kidney / Q000166:cytology; D008954:Models, Biological; D019789:Tetraethylammonium / Q000494:pharmacology; D013997:Time Factors; D010130:p-Aminohippuric Acid / Q000494:pharmacology
chemical_list: D004151:Dipeptides; C004194:glycylsarcosine; D019789:Tetraethylammonium; D002506:Cephalexin; D010130:p-Aminohippuric Acid