title: Comparative studies on in vitro methods for evaluating in vivo function of MDR1 P-glycoprotein.
abstract: OBJECTIVE
  MDR1 P-glycoprotein (P-gp) plays an important role in determining drug disposition. The purpose of the present study was to establish in vitro models to predict the in vivo function of P-gp.
  
  
  METHODS
  As an in vitro method, the transcellular transport of 12 compounds across the monolayer of Caco-2- and MDR1-transfected cells was examined. The ability of these compounds to stimulate the ATP hydrolysis was also determined using the isolated membrane fraction expressing P-gp. As a parameter to describe the in vivo P-gp function, we calculated the brain-to-plasma concentration ratio of compounds in mdr1a/1b knockout mice divided by the same ratio in wild type mice.
  
  
  RESULTS
  A good correlation was observed between the in vitro flux ratio across the monolayer and in vivo P-gp function for 12 compounds. Although all compounds that stimulated ATP hydrolysis were significantly transported by P-gp, some compounds were transported by P-gp without significantly affecting ATP hydrolysis.
  
  
  CONCLUSIONS
  Collectively, the in vitro flux ratio across monolayers of P-gp-expressing cells may be used to predict in vivo P-gp function. The extent of ATP-hydrolysis in vitro may also be a useful parameter for in vivo prediction, particularly for eliminating P-gp substrates in high-throughput screening procedures.
authors.affiliation: Graduate School of Pharmaceutical Sciences, The University of Tokyo Hongo, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Adachi
authors.forename: H
authors.initials: H
authors.lastname: Suzuki
authors.forename: Y
authors.initials: Y
authors.lastname: Sugiyama
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000502:physiology*; D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport; D001812:Blood-Brain Barrier / Q000502:physiology*; D018938:Caco-2 Cells; D002463:Cell Membrane Permeability / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D006801:Humans; D006868:Hydrolysis; D018374:LLC-PK1 Cells; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D008954:Models, Biological; D004364:Pharmaceutical Preparations / Q000378:metabolism*; D013552:Swine; D014018:Tissue Distribution; D014162:Transfection
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D004364:Pharmaceutical Preparations; D000255:Adenosine Triphosphate