Lysosomal Changes of Retinal Pigment Epithelium

ABSTRACT

This study was carried out to investigate diurnal changes of lysosomes includ ing ultrastructural changes of phagosomes and activity of acid phosphatase in the phagosomes and diurnal biochemical changes of cathepsin D activity of rab bits. The eyes were obtained at 000, 400, 800, 1200, 1600 and 2000 o'clock. The number of lysosomes and phagosomes in retinal pigment epithelium(RPE) was the highest at 800 o'clock, thereafter decreased with time. There were three types of phagosomes; fresh phagosomes showed both negative and positive reactions, lamellar bodies positive, and dense bodies partially positive. The biochemical activity of cathepsin D was the highest at 800 o'clock consistent with the time of peak in phagocytic activities of RPE. According to the above results, it would be suggested that the maximum shedding of outer segments and phagocytic activity of RPE occurred on the early stage after sunlight exposure, and that the phagosomes were degraded to the lamellar bodies and dense bodies sequentially. And also activity of the cathepsin D would be increased consistent with the phagocytic activity of RPE.