Some observations in the fine structure of age changes of the mouse retinal pigment epithelium.

Age changes of the fine structure in the CF-1 mouse retinal pigment epithelium were studied from 1--24 months old. The change most characteristic of the senescence of the retinal pigment epithelium was found to be the appearance of wavy undulating 12nm wide filaments having a periodicity of about 80nm after the 12th month. In addition, the retinal pigment epithelial cells of the aging eye were found to have a marked accumulation of lysosomal dense bodies measuring about 0.3 to 1.2 micrometer in diameter especially in the apical portion of the cytoplasm. Extended and enlarged basal cytoplasmic infoldings of the retinal pigment epithelial cells were another prominent age change in the old mouse. In these basal infoldings densely fixed amorphous materials by tannic acid and very fine filaments are recognized. Age-related changes of the retinal pigment epithelial cell of the CF-1 mouse may take place as the degeneration of cytoplasmic materials, the appearance of bundles consisting of parallel undulating filaments, and the extending process of basal infolding from the choroid side.