Extrusion of lysosomal bodies from apical mouse retinal pigment epithelium.

The retinal pigment epithelium (RPE) of 1- 24-month-old CF-1 mice was examined by both light and electron microscopy. Measurement of the area occupied by lysosomal bodies was carried out using a semiautomatic quantitative picture analyzing system (Kontron-EKO). Accumulation of lysosomal bodies in the apical RPE cytoplasm was the most characteristic feature in eyes over 12 months of age. The relative volume of lysosomal bodies to each RPE cytoplasm was maximal in 24-month-old mice RPE, approximately three times that of 3-month-old mice. Complicated lysosomal bodies and small lysosomal bodies were also observed in the dilated microvilli, in the apices of the apical RPE cytoplasm and in the subretinal spaces in eyes over 18 months of age. The passway and extrusive mechanism of lysosomal bodies are discussed.