Lutein and zeaxanthin are associated with photoreceptors in the human retina

Purpose. Previous studies showed that lutein and zeaxanthin, the major huma n retinal carotenoids, are concentrated in the macula. In this study, the c arotenoids in human macular and peripheral retina and the retinal pigment e pithelium (RPE) were analyzed. They were also determined in the rod outer s egments (ROS) before and after removal of extrinsic membrane proteins. Methods. Carotenoids were extracted from the macular and peripheral section s of human retina and RPE with hexane in dim light and analyzed by high per formance liquid chromatography (HPLC). ROS samples equivalent to the amount in a single retina were also analyzed. Results. Retinal carotenoid amounts were similar to previous reports, but o nly low levels were detected in the RPE. Regional ratios of lutein:zeaxanth in were similar in the retina and RPE. Approximately 25% of the total retin al carotenoids were found in the ROS, indicating that a substantial portion of peripheral retinal carotenoids are present in the ROS. However, after r emoval of the extrinsic membrane proteins and subsequent analysis, caroteno ids were not detected. Conclusions: Most of the carotenoids in the human peripheral retina are pre sent in the ROS. These ROS carotenoids are associated with soluble or salt- dependently bound proteins.