Integrity of the blood-aqueous barrier in hyperuricemia.

Neither the origin nor the role of high levels of uric acid, found in the aqueous humor of some human glaucomatous eyes, is known. A model of hyperuricemia in the rat was evaluated for its contribution to urate levels in the aqueous humor. Epinephrine-induced hyperuricemia in male rats was shown to increase mean serum urate levels from 1.2 mg/dL to 6.7 mg/dL. Female rats were shown to have a lower uric acid baseline and a lower absolute hyperuricemic level than males. The mean aqueous-humor urate levels were increased from 0.06 mg/dL to 0.33 mg/dL for male rats. In our studies, the blood-aqueous barrier effectively prevented equilibration between the systemic and ocular compartments. The increased aqueous-humor uric acid levels in glaucoma may arise from intraocular mechanisms.