Binding of retinol to isolated retinal pigment epithelium in the presence and absence of retinol-binding protein.

Isolated human and bovine pigment epithelium actively binds H3-retinol when vitamin A alcohol is present in the incubation medium bound to human retinol-binding protein. Pigment epithelium is unable to bind retinol present in the incubation solution as the free form, i.e., not bound to its physiologic carrier protein. It is suggested that an interaction between retinol-binding protein and the membranes of pigment epithelial cells is essential for the active transport of retinol into pigment epithelium.