The source of protein in the aqueous humor of the normal monkey eye

In vivo aqueous fluorophotometry, morphology, and computational modeling were combined to examine the source of protein and the pathway by which protein enters the aqueous humor of monkeys. A computational model was developed to determine the likelihood of a diffusional route for delivering plasma proteins from ciliary body capillaries via the iris to anterior chamber aqueous humor, bypassing the posterior chamber. Model predictions were compared to aqueous fluorophotometric data obtained from monkeys following a single intravenous injection of fluoresceinated horseradish peroxidase (F-HRP, 250 mg/kg body mass). Model predictions of the magnitude and time course of anterior chamber F-HRP concentration agree with the fluorophotometric measurements. For example, of anterior chamber F-HRP concentration as a percentage of initial plasma F-HRP concentration at 90 min and 180 min post-injection was predicted to be 0.02% and 0.05%, respectively, and was measured to be 0.01-0.03% and 0.03-0.06%, respectively. In addition, model predictions in the case of a constant plasma protein level also are consistent with experimental data. The steady-state anterior chamber total protein concentration as a percentage of plasma protein concentration was predicted to be 0.2% and was assayed to be 0.05-0.2%. As in our previous study of the normal rabbit eye, morphologic and tracer localization evidence combined with the good agreement between model predictions and experimental data lead to the conclusion that a significant amount of the plasma protein normally present in monkey aqueous humor originates in ciliary body capillaries and diffuses anteriorly through the iris and into the anterior chamber.