Phagocytic activity in the ischemic retinal pigment epithelial cells. An electronmicroscopic histochemical study of acid phosphatase.

The role of lysosomal enzymes in ischemic retinal pigment epithelial cells (RPE) of albino rabbits was examined with the modified Gomori technique for acid phosphatase. Ischemia was produced by cutting the lateral posterior ciliary artery and short posterior ciliary arteries (PCA). Five days after PCA-cut RPE in the ischemic region were disorganized by increased enzymatic digestion. In RPE of the border between the ischemic and normal region a lot of fragmented outer segments were phagocytosed 24 h to 7 days after PCA-cut. At this time phagosomes appeared much more frequently than in the normal retina, showing several variations in their shape, localization, and histochemical reaction. However, after 10 and 14 days, RPE in the border had a tendency to reduce the phagocytic activity. A strong acid phosphatase activity was encountered in the phagosomes of macrophages, which was considered to be derived from RPE, and seemed to play the major role in scavenging destructed retinal elements.