title: Caco-2 cells and Biopharmaceutics Classification System (BCS) for prediction of transepithelial transport of xenobiotics (model drug: caffeine).
abstract: OBJECTIVE
  The Caco-2 cell monolayer model is widely used as a standard screening tool for studying the mechanisms of cellular drug transport. Caffeine was chosen as a model drug and is supposed to be class I of the Biopharmaceutics Classification System (BCS). Our study was conducted 1) to characterize the mechanisms of caffeine transport across the intestinal barrier, 2) to classify caffeine according to BCS, 3) to predict drugs intestinal absorption in humans.
  
  
  METHODS
  Caffeine transport (0.1, 0.3, 1 and 10 mmol/l) was studied in Caco-2 cell monolayer in apical to basolateral (AP-BL) and basolateral to apical (BL-AP) direction, under iso-pH 7.4 and pH-gradient (6/7.4) conditions. The relative contribution of the paracellular route was estimated using Ca2+- free transport medium (opening tight junctions).
  
  
  RESULTS
  The caffeine transport was linear with time, transport direction and pH independent, displaying non-saturable (first-order) kinetics, with high permeability coefficient (Papp): in AP-BL direction Papp = 46.3-53.5 x 10-6 cm/s; in BL-AP direction Papp = 45.6-49.4 x 10-6 cm/s. Thus, the transport seems to be transcellular mediated by passive diffusion. Using Ca2+- free transport medium tight junctions were opened (confirmed by increased Papp of mannitol) but the caffeine Papp was not changed. Thus, the paracellular route is only a minor way of caffeine transport.
  
  
  CONCLUSIONS
  High solubility and high permeability of caffeine rank it among class I of BCS and well absorbed compounds.
authors.affiliation: Institute of Experimental Biopharmaceutics, Czech Academy of Sciences, Czech Republic. smetanova@uebf.cas.cz
authors.forename: Libuse
authors.initials: L
authors.lastname: Smetanova
authors.forename: Vera
authors.initials: V
authors.lastname: Stetinova
authors.forename: Dagmar
authors.initials: D
authors.lastname: Kholova
authors.forename: Jaroslav
authors.initials: J
authors.lastname: Kvetina
authors.forename: Jan
authors.initials: J
authors.lastname: Smetana
authors.forename: Zbynek
authors.initials: Z
authors.lastname: Svoboda
mesh_terms: D001692:Biological Transport / Q000187:drug effects* / Q000502:physiology*; D018938:Caco-2 Cells; D002110:Caffeine / Q000493:pharmacokinetics* / Q000494:pharmacology; D018929:Cell Culture Techniques; D002470:Cell Survival / Q000187:drug effects; D004058:Diffusion; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007408:Intestinal Absorption; D007413:Intestinal Mucosa / Q000378:metabolism*; D007700:Kinetics; D016014:Linear Models; D008353:Mannitol / Q000378:metabolism; D010539:Permeability / Q000187:drug effects; D019108:Tight Junctions / Q000187:drug effects / Q000378:metabolism; D015262:Xenobiotics / Q000493:pharmacokinetics* / Q000494:pharmacology
chemical_list: D015262:Xenobiotics; D002110:Caffeine; D008353:Mannitol