Electron-opaque inclusions in the rat retinal pigment epithelium after treatment with chelators of zinc.

Sprague-Dawley male rats given intraperitoneal injections of zinc chelators, namely dithizone and 1,10-phenanthroline, had unusual osmiophilic inclusion bodies in their retinal pigment epithelium (RPE). These structures were not seen in untreated or vehicle-treated controls. The morphology of the inclusion bodies clearly distinguished them from cytoplasmic organelles observed normally in the RPE. The number of inclusion bodies is dose-dependent. The bodies do not have the morphological characteristics of lipid droplets seen infrequently in the untreated rat RPE. The results suggest that sequestration of zinc, either rapidly with injections of dithizone or more slowly with daily administration of 1,10-phenanthroline, exerts pronounced effects on the retinal pigment epithelial cells.