title: Lutein and zeaxanthin are associated with photoreceptors in the human retina.
abstract: OBJECTIVE
  Previous studies showed that lutein and zeaxanthin, the major human retinal carotenoids, are concentrated in the macula. In this study, the carotenoids in human macular and peripheral retina and the retinal pigment epithelium (RPE) were analyzed. They were also determined in the rod outer segments (ROS) before and after removal of extrinsic membrane proteins.
  
  
  METHODS
  Carotenoids were extracted from the macular and peripheral sections of human retina and RPE with hexane in dim light and analyzed by high performance 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 only low levels were detected in the RPE. Regional ratios of lutein:zeaxanthin were similar in the retina and RPE. Approximately 25% of the total retinal carotenoids were found in the ROS, indicating that a substantial portion of peripheral retinal carotenoids are present in the ROS. However, after removal of the extrinsic membrane proteins and subsequent analysis, carotenoids were not detected.
  
  
  CONCLUSIONS
  Most of the carotenoids in the human peripheral retina are present in the ROS. These ROS carotenoids are associated with soluble or salt-dependently bound proteins.
authors.affiliation: University of Texas Medical Branch, Department of Ophthalmology & Visual Sciences TX, Galveston 77555-1067, USA.
authors.forename: O G
authors.initials: OG
authors.lastname: Sommerburg
authors.forename: W G
authors.initials: WG
authors.lastname: Siems
authors.forename: J S
authors.initials: JS
authors.lastname: Hurst
authors.forename: J W
authors.initials: JW
authors.lastname: Lewis
authors.forename: D S
authors.initials: DS
authors.lastname: Kliger
authors.forename: F J
authors.initials: FJ
authors.lastname: van Kuijk
mesh_terms: D002338:Carotenoids / Q000032:analysis; D002851:Chromatography, High Pressure Liquid; D006801:Humans; D014975:Lutein / Q000032:analysis*; D010786:Photoreceptor Cells / Q000737:chemistry*; D010857:Pigment Epithelium of Eye / Q000737:chemistry; D012160:Retina / Q000737:chemistry*; D012374:Rod Cell Outer Segment / Q000737:chemistry; D024341:Xanthophylls; D065146:Zeaxanthins; D019207:beta Carotene / Q000031:analogs & derivatives* / Q000032:analysis
chemical_list: D024341:Xanthophylls; D065146:Zeaxanthins; D019207:beta Carotene; D002338:Carotenoids; D014975:Lutein