Ultrastructural localization of lipid peroxides as benzidine-reactive substances in the albino mouse eye

Lipid peroxidation is considered to be a prominent feature of retinal degeneration and has also been proposed to be involved in the pathogenesis of age-related macular degeneration. Melanin protects against lipid peroxidation and takes part in the detoxification of lipid peroxides (LP). LP can be ultrastructurally detected as benzidine-reactive substances (BRS) using tetramethylbenzidine (TMB). Albino mice lack melanin. In the present study, LP were localized as BRS in the eyes of albino and pigmented mice. Eye cups of an albino mouse lineage and of wild-type mice were fixed with 2% glutaraldehyde, incubated with 0.5 mg/ml TMB and embedded for electron microscopy. BRS were detected in the eyes of albino mice, but no reaction product was seen in pigmented eyes. BRS located in the retinal pigment epithelium (RPE) and in the choroid of the albino mouse; no BRS were found in intact rod outer segments (ROS). The lack of melanin in albino mice is associated with a higher level of lipid peroxidation in RPE and choroid. Melanin seems to protect against LP in RPE and choroid. A lack of melanin is not associated with lipid peroxidation in intact ROS. The present investigation demonstrates the significance of melanin in protection against LP in RPE and choroid.