Localization of peroxidase activity in the retina and the retinal pigment epithelium of the Syrian golden hamster (Mesocricetus auratus).

1. Endogenous peroxidase was localized by electron microscopy within the retinal tissue of the golden Syrian hamster. 2. Peroxidase activity was found in the apical parts of rod outer segments, in the cytoplasm and phagosomes of the retinal pigment epithelium (RPE), and extracellularly between the basal infoldings of the RPE. 3. No reaction product was detected when either H2O2 or tetramethyl benzidine were omitted from the reaction medium. 4. The same was true when the tissue was osmicated before the incubation in the reaction medium or treated with 100 mM sodium azide. 5. These results indicate that the peroxidatic activity was enzymatically mediated.