STUDIES ON RETINA AND PIGMENT EPITHELIUM IN HEREDITARY CANINE CEROID LIPOFUSCINOSIS .1. DISTRIBUTION OF ENZYMES IN WHOLE RETINA AND PIGMENT EPITHELIUM

Abstract

The massive accumulation of autofluorescent lipopigments, representative of autoxidation, is a key morphological feature in canine ceroid lipofuscinosis (CCL). In the eye peroxidase, catalase and 4 acid hydrolases were compared with regard to age and clinical condition in a series of English setters affected with CCL. In unaffected English setters soluble peroxidase increased in the RPE [retina and pigment epithelium] to adult levels at 2 yr of age. Affected dogs had higher RPE peroxidase activity earlier in life, which then declined with age. The soluble retinal peroxidase of unaffected and CCL dogs increased steadily with age, but the latter group of dogs were much lower in activity. By 2 yr of age, RPE and retinal peroxidase values were only 25% and 47% of unaffected dog levels. Although the soluble enzyme of unaffected dogs exhibited a maturational profile, membrane-bound RPE peroxidase showed a hyperbolic curve reaching a maximum at 10 mo. of age. By 2 yr of age, the bound enzyme in affected dogs was below unaffected levels in the RPE and retina. Three acid hydrolases were slightly increased in the RPE and retina of affected dogs. Acid lipase activity was similar in unaffected and CCL dogs. Catalase was not found in the RPE of either group of dogs. The catalase activity in the retina of affected and unaffected dogs was at similar levels. Since catalase is not present in the RPE, the major defense against peroxidase accumulation and peroxide toxicity probably depends upon peroxidase. A decrease in this key regulating enzyme may be related to the formation of lipopigments in the retina and RPE of dogs with CCL.