title: Mechanisms of transport and structure-permeability relationship of sulfasalazine and its analogs in Caco-2 cell monolayers.
abstract: OBJECTIVE
  To investigate the mechanisms involved in transport of sulfasalazine in Caco-2 cells.
  
  
  METHODS
  Permeability coefficients of sulfasalazine and its analogs across Caco-2 cell monolayers were measured as a function of direction of transport, energy and concentration dependence, and in the presence of inhibitors of various cellular efflux pumps and transporters.
  
  
  RESULTS
  Permeability coefficients of sulfasalazine across Caco-2 cell monolayers were approximately 342-, 261-, and 176-fold higher from basolateral to apical direction (BL-->AP) than from apical to basolateral direction (AP-->BL) at 100, 200, and 500 microM, respectively. Carrier permeability coefficient, non-saturable membrane permeability coefficient, and Michaelis constant were estimated to be 1.4x10(-5) cm/s, 1.9x10(-8) cm/s, and 369 microM, respectively. The efflux of sulfasalazine was completely blocked at 4 degrees C and in the presence of an uncoupler of oxidative phosphorylation. Using cellular efflux inhibitors, the permeability of sulfasalazine was shown to depend on multidrug resistance-associated protein and anion sensitive transport mechanisms. Structure-permeability studies showed that the affinity of sulfasalazine for the cellular efflux pumps and transporters in Caco-2 cells depended strongly on the carboxylic acid functional group.
  
  
  CONCLUSIONS
  The permeability of sulfasalazine across Caco-2 cell monolayer is very low due to its strong interaction with multiple cellular efflux pumps and transporters. This may partially explain its low absorption in vivo.
authors.affiliation: Pharmaceutics Department, Boehringer Ingelheim Pharmaceuticals, Inc, Ridgefield, CT 06877, USA.
authors.forename: E
authors.initials: E
authors.lastname: Liang
authors.forename: J
authors.initials: J
authors.lastname: Proudfoot
authors.forename: M
authors.initials: M
authors.lastname: Yazdanian
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000037:antagonists & inhibitors / Q000378:metabolism; D018528:ATP-Binding Cassette Transporters / Q000037:antagonists & inhibitors / Q000378:metabolism; D027321:Anion Transport Proteins; D001693:Biological Transport, Active / Q000187:drug effects; D018938:Caco-2 Cells / Q000187:drug effects / Q000378:metabolism*; D002352:Carrier Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D002463:Cell Membrane Permeability / Q000187:drug effects / Q000502:physiology; D003080:Cold Temperature; D004734:Energy Metabolism; D005765:Gastrointestinal Agents / Q000493:pharmacokinetics*; D006801:Humans; D007408:Intestinal Absorption / Q000187:drug effects / Q000502:physiology; D007700:Kinetics; D019804:Mesalamine / Q000493:pharmacokinetics; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D013329:Structure-Activity Relationship; D013427:Sulfapyridine / Q000493:pharmacokinetics; D012460:Sulfasalazine / Q000031:analogs & derivatives* / Q000493:pharmacokinetics*
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D018528:ATP-Binding Cassette Transporters; D027321:Anion Transport Proteins; D002352:Carrier Proteins; D005765:Gastrointestinal Agents; D019804:Mesalamine; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D013427:Sulfapyridine; D012460:Sulfasalazine