Histochemical localization of catalase in cultured lens epithelial cells

The diaminobenzidine (DAB) technique was used to investigate the localization of the peroxidatic activity of catalase in cultured lens epithelial cells at the ultrastructural level. Cultured rabbit, bovine and mouse lens epithelial cells incubated in an alkaline DAB reaction mixture contained catalase-positive microperoxisomes which were randomly distributed throughout the cytoplasm. The reaction product of catalase was abolished when cells were treated with 3-amino-1-H-1,2,4-triazole, a specific inhibitor of catalase, and was not detected when DAB or H2O2 was omitted from the incubation medium, or when the pH of the reaction mixture was lowered to 7.0. The fine structure of lens epithelial cells that were constantly exposed to 0.025 or 0.05 mM hydrogen peroxide was also determined. Lens epithelial cells that were constantly exposed to 0.05 mM H2O2 for 1-3 h exhibited damaged mitochondria, a phenomenon that did not occur when the cells were exposed to 0.025 mM peroxide.