Retinol receptors in corneal epithelium, stroma and endothelium

Specific receptors for retinol are present in the cytosol fraction of corneal epithelium as demonstrated by sucrose density gradient centrifugation. These appear to be (1) protein in nature (2) of small molecular size (2 S) (3) specific for retinol and (4) present in several species. Assuming a receptor molecular weight of 15 000 and a single mole of retinol bound/mole of receptor protein, the association constant value is 5.26-10(7) with deltaG degrees = -8.53 kcal/mol. 2-S receptors are also observed in stroma and endothelium along with another binding species of approximately 8 S. Binding of [3H]retinol in bovine epithelial cytosol can also be demonstrated by disc gel electrophoresis and gel filtration. Immunodiffusion techniques demonstrate that monkey corneal epithelial and stromal cytosol samples do not contain contaminating serum retinol binding-protein.