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N.P. S. Cheruvu, E.R. Escobar, U.B. Kompella; Transscleral Transport: Barrier Properties of Sclera, Choroid–Tapetum, and Retinal Pigment Epithelium . Invest. Ophthalmol. Vis. Sci. 2005;46(13):5390.
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© ARVO (1962-2015); The Authors (2016-present)
To assess the influence of various underlying tissue layers on in–vitro solute transport across bovine sclera.
The in vitro permeabilities of 3H–mannitol (log P = –3.10), sodium fluorescein (log P = –0.97), and rhodamine 6G (log P = 4.20) were measured for bovine sclera, sclera–choroid–tapetum, and sclera–choroid–RPE in the episcleral to vitreal direction using modified Ussing chambers (n=6). All solutions were made in a physiological assay buffer without any adjuvants. For the isolation of sclera–choroid–tapetum–RPE, the neural retina was removed by exposing the eye cup to the assay buffer. For the isolation of sclera–choroid–tapetum, the retinal pigment epithelium (RPE) in the above preparation was removed by exposing a hypertonic solution. The removal of RPE was confirmed using TEM. For the isolation of sclera, the underlying tissues were gently scraped off. The donor solutions for transport studies contained 3H–mannitol (1 µCi/ml), sodium fluorescein (36.3 or 500 µg/ml), or rhodamine 6G (100 µg/ml) in assay buffer. Solute concentrations in the receiver chamber were determined using a liquid scintillation counter for 3H–mannitol and a spectrofluorometer for sodium fluorescein and rhodamine 6G. The permeability co–efficients (rate of transport normalized to surface area and donor solute concentration) for the choroid–tapetum and RPE were calculated from the measured permeability co–efficients of sclera, sclera–choroid–tapetum and sclera–choroid–tapetum–RPE using the following equation: 1/Papp(B) = [1/Papp(AB)]– [1/Papp(A)]
The permeability co–efficients (Papp) for the three solutes across bovine sclera, choroid–tapetum and RPE layers are summarized below:
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