title: Ciliary muscle capillaries have blood-tissue barrier characteristics.
abstract: It was determined whether the capillaries in the ciliary muscle are of the blood-tissue barrier or of the permeable non-barrier type. Ciliary body and iris of normal human and animal eyes were examined by electron microscopy and by immunohistochemical staining with a panel of antibodies recognizing endothelial blood-brain barrier markers. In addition, horseradish peroxidase (HRP) tracer studies of the anterior segment were carried out in rabbits. Our results demonstrated that the capillary endothelium in human and rabbit ciliary muscle has few luminal pinocytotic vesicles and a morphological aspect suggesting the presence of tight junctions. Ciliary muscle and iris capillaries stained positive for the blood-brain barrier markers Glucose-Transporter-1 and P-Glycoprotein, while staining for the PAL-E antigen and the transferrin receptor was absent. In the rabbit ciliary muscle, vascular leakage of exogenous HRP tracer was absent. It was concluded that this functional barrier and the observed phenotype of ciliary muscle capillaries are consistent with a blood-tissue barrier function similar to that of the iris microvasculature.
authors.affiliation: Department of Ophthalmology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: R O
authors.initials: RO
authors.lastname: Schlingemann
authors.forename: P
authors.initials: P
authors.lastname: Hofman
authors.forename: J
authors.initials: J
authors.lastname: Klooster
authors.forename: H G
authors.initials: HG
authors.lastname: Blaauwgeers
authors.forename: R
authors.initials: R
authors.lastname: Van der Gaag
authors.forename: G F
authors.initials: GF
authors.lastname: Vrensen
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D015415:Biomarkers / Q000032:analysis; D002196:Capillaries / Q000378:metabolism; D002417:Cattle; D002924:Ciliary Body / Q000098:blood supply* / Q000378:metabolism / Q000648:ultrastructure; D004730:Endothelium, Vascular / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D007365:Intercellular Junctions / Q000502:physiology*; D007498:Iris / Q000098:blood supply / Q000378:metabolism / Q000648:ultrastructure; D008252:Macaca fascicularis; D008854:Microscopy, Electron; D008875:Middle Aged; D011817:Rabbits; D012756:Sheep
chemical_list: D015415:Biomarkers