Figure 9.

Possible mechanism for AsA transport in human ciliary epithelium. Sodium-dependent vitamin C transporter 2, located at PE adjacent to ciliary stroma microvasculature, transports AsA from low concentration in blood plasma to accumulate high concentration in the PE. Then through facilitated diffusion or other unidentified active transporters, AsA may cross through bilayer membranes to NPE, and finally delivered to aqueous humor. Meanwhile, the DHA in the aqueous humor could be transported by GLUT1, which is located adjacent to aqueous humor side, quickly recycling in the ciliary epithelium.