Labeled fucose, heretofore thought to be a cone-specific sugar, has been shown to be incorporated into rhodopsin following intravitreal injection in both beagles and miniature poodles, the latter either normal controls or animals affected with inherited progressive rod-cone degeneration. The radiolabel could be released hydrolytically and was identified chromatographically as fucose. Similarly, labeled palmitic acid was incorporated into rhodopsin following intravitreal injection in beagles as well as both normal and affected poodles. After hydrolytic release, the label was identified as palmitic acid by thin layer chromatography. The posttranslational modification of rhodopsin by the addition of fucose and palmitic acid thus occurs in at least two strains of dogs but does not appear to be altered in the poodles affected with inherited retinal degeneration. However, labeling of phospholipids with palmitic acid in the affected poodles is half as great as in controls. This could be related to the reduced rate of outer segment renewal in the affected animals.
