Ascorbate concentration in tissues from normal and buphthalmic rabbits.

Previous studies show a progressive lowering of ascorbate concentration in the aqueous humor from rabbits with hereditary buphthalmus, depending on the severity of the buphthalmus. In this study, the ascorbate concentration of different tissues from age-matched adult buphthalmic and control rabbits were analyzed to determine whether a defect of ascorbate transport occurs in a variety of tissues from rabbits with hereditary buphthalmus. Our results showed that ascorbate changes were observed only in ocular tissues. The lowering of ascorbate concentration occurs only in lens and cornea, which depend on the aqueous humor to deliver ascorbate from the blood. The tissues that derive ascorbate directly from the blood, such as the ciliary body-iris and retina of buphthalmic eyes, have normal ascorbate concentration. It has been postulated that ascorbate is oxidized in the ciliary body-iris to facilitate its transport across the epithelium. A defect in the buphthalmic eyes to oxidize ascorbate could be the primary cause of lowering ascorbate concentration in the aqueous humor.