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Abstract
The distribution of nonmetabolized carbon 14-labelled α-aminoisobutyric acid (α-AIB) in the anterior segment of the rabbit eye has been determined in vivo. In addition to confirming earlier observations of the active accumulation of the molecule by the lens, the distribution in the cornea was found to favor the hypothesis of passive diffusion through the corneal endothelial layer and active uptake by the epithelium. The passive role of the endothelium was shown also by measuring the flux of α-AIB across the anterior stromal surface. This flux was substantially greater in the absence of endothelium. The active accumulation of α-AIB by the corneal epithelium occurred only when the molecule was present on the stromal side. A significant barrier to diffusion as well as no evidence of active uptake teas found when the molecule was present in the tears.