Dynamics of Ascorbate in the Aqueous Humor and Tissues Surrounding Ocular Chambers

Abstract

The level of ascorbate in the aqueous humor and surrounding intraocular structures in enucleated arterially perfused rabbit eye was investigated. The enucleated eye preparation was shown to be capable of secreting ascorbate from the perfusate into the aqueous humor. Ascorbate in the iris, ciliary body and cornea was released into the aqueous humor when the eye was perfused with ascorbate-free solution. Failure to obtain aqueous flow rates from the decay of ascorbate in the anterior chamber was due to the contribution of ascorbate from these ocular tissues during the perfusion. Histochemically, ascorbate was localized in the pigmented epithelial layer in the valleys between the ciliary processes and the pars plana of the ciliary body and in the iris. In the cornea, distinct localization of ascorbate was observed in the endothelium and basal cell layer of the epithelium.

A family of mammalian Na+-dependent L-ascorbic acid transporters

“…4). This SVCT2 distribution was consistent with the known sites of L-ascorbic acid concentration in the rabbit eye 26 , and the characteristics of SVCT2 re¯ected those of a Na + -dependent L-ascorbic acid transport activity expressed in bovine pigmented ciliary epithelial cells 20 . In the rat, SVCT1 (Fig.…”

A family of mammalian Na+-dependent L-ascorbic acid transporters

“…4). This SVCT2 distribution was consistent with the known sites of L-ascorbic acid concentration in the rabbit eye 26 , and the characteristics of SVCT2 re¯ected those of a Na + -dependent L-ascorbic acid transport activity expressed in bovine pigmented ciliary epithelial cells 20 . In the rat, SVCT1 (Fig.…”

Expression Profiling of Ascorbic Acid–Related Transporters in Human and Mouse Eyes

“…Furthermore, SVCT2 located in human pigmented ciliary epithelial cells was mainly distributed around the cellular basal membranes facing the ciliary vessels, whereas human nonpigmented cells did not express SVCT2. Although a few studies reported SVCT2 expression in the ciliary epithelium of rabbit eyes, 3 , 39 , 40 as well as indirect evidence in an in vitro study of bovine ciliary epithelium, 39 this is the first time, to our knowledge, clearly indicating the differences of SVCT2 distribution in human ciliary epithelium as compared with GLUT1 ( Figs. 2 , 3 , 5 , 6 ).…”

Intraocular Oxygen and Antioxidant Status: New Insights on the Effect of Vitrectomy and Glaucoma Pathogenesis

“…Antioxidant enzymes such as superoxide dismutase, glutathione peroxidase, 75 and catalase have also been identified in aqueous humor. In contrast to nocturnal animals, the corneal epithelium, 76,77 lens, 78 vitreous, 9 and aqueous humor 79,80 of diurnal animals contain extremely high levels of AsA compared to that in plasma. 81 Shui and colleagues 8 noted that metabolism of molecular oxygen in the vitreous gel occurs in an AsAdependent manner, without an exogenous catalyst and independent of light, revealing the significance of AsA as a primary regulator of intraocular molecular oxygen.…”

A family of mammalian Na+-dependent L-ascorbic acid transporters

“…4). This SVCT2 distribution was consistent with the known sites of L-ascorbic acid concentration in the rabbit eye 26 , and the characteristics of SVCT2 re¯ected those of a Na + -dependent L-ascorbic acid transport activity expressed in bovine pigmented ciliary epithelial cells 20 . In the rat, SVCT1 (Fig.…”

Expression Profiling of Ascorbic Acid–Related Transporters in Human and Mouse Eyes

“…Furthermore, SVCT2 located in human pigmented ciliary epithelial cells was mainly distributed around the cellular basal membranes facing the ciliary vessels, whereas human nonpigmented cells did not express SVCT2. Although a few studies reported SVCT2 expression in the ciliary epithelium of rabbit eyes, 3 , 39 , 40 as well as indirect evidence in an in vitro study of bovine ciliary epithelium, 39 this is the first time, to our knowledge, clearly indicating the differences of SVCT2 distribution in human ciliary epithelium as compared with GLUT1 ( Figs. 2 , 3 , 5 , 6 ).…”

Intraocular Oxygen and Antioxidant Status: New Insights on the Effect of Vitrectomy and Glaucoma Pathogenesis

“…Antioxidant enzymes such as superoxide dismutase, glutathione peroxidase, 75 and catalase have also been identified in aqueous humor. In contrast to nocturnal animals, the corneal epithelium, 76,77 lens, 78 vitreous, 9 and aqueous humor 79,80 of diurnal animals contain extremely high levels of AsA compared to that in plasma. 81 Shui and colleagues 8 noted that metabolism of molecular oxygen in the vitreous gel occurs in an AsAdependent manner, without an exogenous catalyst and independent of light, revealing the significance of AsA as a primary regulator of intraocular molecular oxygen.…”

A family of mammalian Na+-dependent L-ascorbic acid transporters

“…4). This SVCT2 distribution was consistent with the known sites of L-ascorbic acid concentration in the rabbit eye 26 , and the characteristics of SVCT2 re¯ected those of a Na + -dependent L-ascorbic acid transport activity expressed in bovine pigmented ciliary epithelial cells 20 . In the rat, SVCT1 (Fig.…”

Expression Profiling of Ascorbic Acid–Related Transporters in Human and Mouse Eyes

“…Furthermore, SVCT2 located in human pigmented ciliary epithelial cells was mainly distributed around the cellular basal membranes facing the ciliary vessels, whereas human nonpigmented cells did not express SVCT2. Although a few studies reported SVCT2 expression in the ciliary epithelium of rabbit eyes, 3 , 39 , 40 as well as indirect evidence in an in vitro study of bovine ciliary epithelium, 39 this is the first time, to our knowledge, clearly indicating the differences of SVCT2 distribution in human ciliary epithelium as compared with GLUT1 ( Figs. 2 , 3 , 5 , 6 ).…”

Intraocular Oxygen and Antioxidant Status: New Insights on the Effect of Vitrectomy and Glaucoma Pathogenesis

“…Antioxidant enzymes such as superoxide dismutase, glutathione peroxidase, 75 and catalase have also been identified in aqueous humor. In contrast to nocturnal animals, the corneal epithelium, 76,77 lens, 78 vitreous, 9 and aqueous humor 79,80 of diurnal animals contain extremely high levels of AsA compared to that in plasma. 81 Shui and colleagues 8 noted that metabolism of molecular oxygen in the vitreous gel occurs in an AsAdependent manner, without an exogenous catalyst and independent of light, revealing the significance of AsA as a primary regulator of intraocular molecular oxygen.…”