title: A three-pore model describes transport properties of bovine retinal endothelial cells in normal and elevated glucose.
abstract: OBJECTIVE
  Changes in blood vessel barrier properties contribute to retinal edema in diabetic retinopathy (DR). However, limited data are available to describe the routes of transport for fluids and solutes across the inner blood-retinal barrier (iBRB). In this study, a three-pore model was developed to characterize such routes in normal and elevated glucose levels.
  
  
  METHODS
  Diffusive and apparent permeabilities to TAMRA (467 Da), dextran (70 kDa), and LDL (2000 kDa), as well as hydraulic conductivity, were measured across bovine retinal endothelial cell (BREC) monolayers after exposure to normal- and high-glucose media for 6 days. The data were used to develop a model of transport dynamics. Claudin 5 and eNOS Western blot analysis were used to measure changes in expression and phosphorylation. Immunolocalization of ZO-1 and VE-cadherin demonstrated organization of the junctional complex. Apoptosis was measured by TUNEL assay.
  
  
  RESULTS
  A three-pore model describes the fractional transport of water and molecular tracers across the retinal endothelial barrier. No change in permeability or hydraulic conductivity was observed after exposure to high glucose, whereas VEGF increased permeability in both normal- and high-glucose environments. The transport results were consistent with ZO-1 and VE-cadherin immunocytochemistry and expression of claudin-5, which were all unaltered by high glucose.
  
  
  CONCLUSIONS
  The data describe, for the first time, a model for transport of various size solutes and fluids across endothelial cells of the iBRB. Further, the results support the existence of an indirect pathway by which iBRB permeability is increased through the upregulation of retinal VEGF in response to hyperglycemia.
authors.affiliation: Department of Biomedical Engineering, The City College of The City University of New York, New York, New York 10031, USA.
authors.forename: Sandra V
authors.initials: SV
authors.lastname: Lopez-Quintero
authors.forename: Xin-Ying
authors.initials: XY
authors.lastname: Ji
authors.forename: David A
authors.initials: DA
authors.lastname: Antonetti
authors.forename: John M
authors.initials: JM
authors.lastname: Tarbell
mesh_terms: D000818:Animals; D017209:Apoptosis; D001693:Biological Transport, Active; D001813:Blood-Retinal Barrier / Q000502:physiology*; D015153:Blotting, Western; D001834:Body Water / Q000378:metabolism; D002199:Capillary Permeability / Q000187:drug effects; D002417:Cattle; D002478:Cells, Cultured; D003911:Dextrans / Q000378:metabolism; D004730:Endothelium, Vascular / Q000378:metabolism*; D005947:Glucose / Q000494:pharmacology; D006943:Hyperglycemia / Q000378:metabolism*; D020287:In Situ Nick-End Labeling; D008077:Lipoproteins, LDL / Q000378:metabolism; D008954:Models, Biological; D052250:Nitric Oxide Synthase Type III / Q000378:metabolism; D016133:Polymerase Chain Reaction; D012171:Retinal Vessels / Q000166:cytology / Q000378:metabolism*; D012235:Rhodamines / Q000378:metabolism; D042461:Vascular Endothelial Growth Factor A / Q000494:pharmacology
chemical_list: C114557:5-carboxytetramethylrhodamine succinimidyl ester; D003911:Dextrans; D008077:Lipoproteins, LDL; D012235:Rhodamines; D042461:Vascular Endothelial Growth Factor A; D052250:Nitric Oxide Synthase Type III; D005947:Glucose