Distribution of ascorbate in the retina, subretinal fluid and pigment epithelium

Abstract

The posterior segment of the eye was divided into four compartments: retinal cytosol (R), subretinal fluid on the retinal surface (S/R), retinal pigment epithelial (RPE) cytosol, and subretinal fluid on the RPE surface (S/RPE). The volume of each compartment was estimated from the dilution of creatinine (in the extraction buffer) by the endogenous tissue fluid. The ascorbate concentrations in R, S/R, S/RPE, and RPE were 20.6, 12.3, 3.7, and 5.8 mg/dl respectively. Dehydroascorbate was observed only in the RPE and S/RPE. The decreasing ascorbate concentration from the retina to RPE, and the distribution of dehydroascorbate suggest a movement of ascorbate from the vitreous cavity into the subretinal space. The permeability of retinal cell layers to ascorbate was confirmed by the high radioactivity observed in the subretinal space after an intravitreal injection of C14-ascorbate. The occurrence of dehydroascorbate in the RPE and the S/RPE indicates the presence of oxidative reaction of ascorbate in these compartments, where light induced free radicals are located.

Fourth module of Xenopus interphotoreceptor retinoid-binding protein: activity in retinoid transfer between the retinal pigment epithelium and rod photoreceptors

“…[1][2][3][4] Its concentration in the matrix may be estimated from the amount of IRBP in the eye and volume of the subretinal space to be between 20 and 100 M in mammals. [5][6][7][8] IRBP is thought to play a critical role in mediating the transport of retinoids between the rod photoreceptors and RPE. The role of IRBP in the retinoid visual cycle has been recently reviewed.…”

Vitreous humor and albumin augment the proliferation of cultured retinal precursor cells

“…In the vitreous cavity, the collagen and hyaluronic acid that make up the gel phase of the vitreous remain trapped in situ as a result of inherent physical characteristics, whereas the smaller molecular constituents are ultimately drawn through the interstices of the neural retina as part of the The first two authors contributed equally to this work. bulk flow generated by the active clearing of fluid from the subretinal space by the retinal pigment epithelium (RPE; Lai et al, 1986;Marmor, 1990). These smaller molecules therefore contribute to the local microenvironment of not only the vitreous cavity but, to some extent, the retina and subretinal space as well.…”

“…Despite the potential for overlap in the molecular species present in both the vitreous and subretinal space, these microenvironments generally differ in terms of the relative concentration of small molecules (Lai et al, 1986;Lutty et al, 1996;Saint-Geniez and D'Amore, 2004) as well as a multitude of other considerations, all of which could potentially play a role in determining donor cell engraftment following transplantation. In previous work, we have shown that aqueous humor augments the growth of cultured rat retinal precursor cells when added as a supplement to epidermal growth factor (EGF)-containing proliferation medium (Yang et al, 2006a).…”

Investigation of Laser-Induced Retinal Damage: Wavelength and Pulsewidth Dependent Mechanisms

“…Under normal conditions, we found that ascorbic acid exists in the reduced form in the neural retina and aqueous humor, but mostly in the oxidized form (dehydroascorbic acid, or DHA) in the RPE and choroid (19,30). After a period of light stress, the amount of reduced ascorbic acid declined in the retina while DHA in the RPE and choroid increased.…”