PURPOSE: To determine whether aging is accompanied by changes in aerobic photoreactivity of retinal pigment epithelial (RPE) melanosomes isolated from @entity1 donors of different ages, and to compare the photoreactivity of aged melanosomes with that of RPE @entity6973 . METHODS: @entity1 RPE pigment granules were isolated from RPE cells pooled into groups according to the age of the donors. Photoreactivity was determined by blue-light-induced @entity26 uptake and photogeneration of reactive @entity26 species. Short-lived radical intermediates were detected by spin-trapping, @entity273 by an oxidase electrode, singlet @entity26 by @entity165 assay, and lipid @entity8415 by iodometric assay. RESULTS: Blue-light photoexcitation of melanosomes resulted in age-related increases in both @entity26 uptake and the accumulation of @entity224 anion spin adducts. The efficiencies of these processes, however, were still significantly lower than that induced by photoexcited @entity6973 . During irradiation of melanosomes, a substantial amount of @entity26 was converted into @entity273 , whereas for @entity6973 , @entity273 accounted for not more than 3% of @entity26 consumed. In contrast to @entity6973 , photoexcited melanosomes did not substantially increase the rate of oxidative reactions in the presence of polyunsaturated lipids or albumin. However, @entity26 uptake was significantly elevated in the presence of @entity9050 . Thus, the rate of photo-induced @entity26 uptake in samples containing both @entity9050 and melanosomes approached that observed in @entity6973 samples. CONCLUSIONS: Blue-light-induced photoreactivity of melanosomes increases with age, perhaps providing a source of reactive @entity26 species and leading to depletion of vital cellular reductants, which, together with @entity6973 , may contribute to cellular dysfunction.

Photoreactivity of aged @entity1 RPE melanosomes: a comparison with XXXX .

@entity1 :: ('9606', 'Species') :: ['human', 'Human'] @entity8415 :: ('CHEBI:35924', 'Chemical') :: ['hydroperoxides'] @entity26 :: ('MESH:D010100', 'Chemical') :: ['oxygen'] @entity6973 :: ('MESH:D008062', 'Chemical') :: ['lipofuscin'] @entity273 :: ('MESH:D006861', 'Chemical') :: ['hydrogen peroxide'] @entity224 :: ('MESH:D013481', 'Chemical') :: ['superoxide'] @entity9050 :: ('CHEBI:38290', 'Chemical') :: ['ascorbate'] @entity165 :: ('MESH:D002784', 'Chemical') :: ['cholesterol']
@entity6973 :: (MESH:D008062,Chemical) :: ['lipofuscin']
