title: Unconjugated bilirubin efflux by bovine brain microvascular endothelial cells in vitro.
abstract: OBJECTIVE
  The passage of unconjugated bilirubin (UCB) across the blood-brain barrier into the central nervous system is a crucial first step in the development of kernicterus. The objective of the current study was to characterize the passage of UCB across primary bovine brain microvascular endothelial cell (BBMVEC) monolayers in vitro.
  
  
  METHODS
  Experimental study.
  
  
  METHODS
  Research institute.
  
  
  METHODS
  BBMVECs.
  
  
  METHODS
  Tritiated UCB (H-UCB) transport at 60, 80, 100, 200, 300, and 400 nM concentrations was tested in both the apical to basolateral (A--> B) and basolateral to apical (B-->A) directions in BBMVEC monolayers in vitro with or without preincubation with pharmacologic active transport inhibitors cyclosporine A, indomethacin, or MK571.
  
  
  RESULTS
  The rate of H-UCB transport in the B-->A direction was 6.2- to 7.3-fold higher than in the A-->B direction, suggesting active efflux of UCB. Cyclosporine A (5 microM), a model inhibitor of P-glycoprotein, enhanced A-->B while decreasing B-->A UCB transport, resulting in an overall decrease in BBMVEC UCB efflux of between 46% and 54%. Indomethacin (10 microM) and MK-571 (50 microM), respectively a substrate and potent inhibitor of multidrug resistance-associated protein-1, had no effect.
  
  
  CONCLUSIONS
  We conclude that 1) UCB is transported by BBMVEC monolayers in vitro in a net B-->A direction (i.e., active efflux); and 2) cyclosporine A partially inhibits such transport. We speculate that the blood-brain barrier limits the passage and central nervous system retention of UCB by active transport and that this may be accounted in part by P-glycoprotein.
authors: Department of Pediatrics, University of Pittsburgh School of Medicine, Magee-Womens Research Institute, Pittsburgh, PA, USA.
authors: Deryk
authors: D
authors: Sequeira
authors: Jon F
authors: JF
authors: Watchko
authors: Monica J
authors: MJ
authors: Daood
authors: Terrence L
authors: TL
authors: O'Day
authors: Burhan
authors: B
authors: Mahmood
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000008:administration & dosage / Q000378:metabolism*; D001663:Bilirubin / Q000008:administration & dosage / Q000378:metabolism*; D001692:Biological Transport / Q000187:drug effects; D001812:Blood-Brain Barrier / Q000378:metabolism; D015153:Blotting, Western; D001921:Brain / Q000098:blood supply*; D002417:Cattle; D042783:Endothelial Cells / Q000187:drug effects / Q000378:metabolism*; D066298:In Vitro Techniques; D007647:Kernicterus
chemical_list: D000975:Antioxidants; D001663:Bilirubin