Retinyl esters in the vertebrate neuroretina

High-performance liquid chromatography (HPLC) was employed to measure retinyl esters in the vertebrate retina. Both retina and retinal pigment epithelium (RPE) from frog, chicken, and bovine eyes were studied. In comparison to the RPE, the retina possessed a significant level of 11-cis and all trans retinyl palmitate. Using a sensitive radioassay, we also detected the presence of retinyl ester hydrolase (REH) activity in homogenates prepared from both retina and RPE. The rate of retinyl ester hydrolysis in these retinas was sufficiently high to supply retinal chromophores for the metabolic renewal and for the regeneration of visual pigments. In comparison to retinyl esters in the RPE, retinyl esters in the retina are located much closer to the sites of visual pigment synthesis and regeneration. Hence it is possible that these retinyl esters play a more important role in the visual cycle than those in the RPE.