title: Apparent lack of Mrp1-mediated efflux at the luminal side of mouse blood-brain barrier endothelial cells.
abstract: OBJECTIVE
  The purpose of this work was to determine mrpl-mediated efflux across the luminal membrane of endothelial cells at the blood-brain barrier (BBB) in mice.
  
  
  METHODS
  The transport of radiolabeled etoposide, 17beta-estradiol-D-17beta-glucuronide (E217betaG), vincristine, and doxorubicin across the BBB of mrp1(-/-) and wild-type mice was evaluated by in situ brain perfusion. Etoposide transport was also determined in P-glycoprotein-deficient mdr1a(-/-) mice perfused with both etoposide and mrpl inhibitors like probenecid or MK571. Cerebral vascular volume was determined by co-perfusion with labeled sucrose.
  
  
  RESULTS
  Sucrose perfusion indicated that the vascular space was close to normal in all the studies, indicating that the BBB remained intact. The transport of etoposide, E217betaG, vincristine, and doxorubicin into the brain was not affected by the lack of mrp1. Trans-efflux studies in mrp1-deficient mice with etoposide and E217betaG confirmed that mrpl was not involved in the efflux of these substrates across the BBB. There was also a significant P-gp-mediated efflux of etoposide in studies with P-glycoprotein-deficient mdr1a(-/-) mice. Perfusion of mdr1a(-/-) mice etoposide plus probenecid or MK571 did not affect the brain transport of etoposide.
  
  
  CONCLUSIONS
  Efflux mediated by mrp1 does not seem to occur across the luminal membrane of the endothelial cells forming the mouse BBB.
authors.affiliation: INSERM U26, Hôpital Fernand Widal, 200 Rue du Faubourg Saint-Denis, 75475 Paris cedex 10, France. Salvatore.Cisternino@fwidal.inserm.fr
authors.forename: Salvatore
authors.initials: S
authors.lastname: Cisternino
authors.forename: Christophe
authors.initials: C
authors.lastname: Rousselle
authors.forename: Aurelio
authors.initials: A
authors.lastname: Lorico
authors.forename: Germana
authors.initials: G
authors.lastname: Rappa
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Scherrmann
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism; D000818:Animals; D000972:Antineoplastic Agents, Phytogenic / Q000378:metabolism / Q000494:pharmacology; D001693:Biological Transport, Active / Q000187:drug effects; D001812:Blood-Brain Barrier / Q000187:drug effects*; D019742:Chemokines, CC / Q000235:genetics / Q000502:physiology*; D042783:Endothelial Cells / Q000187:drug effects / Q000378:metabolism*; D004958:Estradiol / Q000494:pharmacology; D005047:Etoposide / Q000378:metabolism / Q000494:pharmacology; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D010477:Perfusion; D011339:Probenecid / Q000494:pharmacology; D011422:Propionates / Q000494:pharmacology; D011804:Quinolines / Q000494:pharmacology; D015262:Xenobiotics / Q000378:metabolism
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000972:Antineoplastic Agents, Phytogenic; D019742:Chemokines, CC; D011422:Propionates; D011804:Quinolines; D015262:Xenobiotics; C070959:Ccl6 protein, mouse; D004958:Estradiol; C059141:verlukast; D005047:Etoposide; D011339:Probenecid