The inner blood-retinal barrier: molecular structure and transport biology.

The inner blood-retinal barrier (inner BRB) is created by complex tight junctions of retinal capillary endothelial cells. Although this barrier prevents the free diffusion of substances between the circulating blood and the neural retina, the inner BRB efficiently supplies nutrients to the retina and removes endobiotics and xenobiotics from the retina to maintain a constant milieu in the neural retina. We review herein the molecular structure and transport mechanism at the inner BRB.