Enzyme activities in human lens epithelium of age-related cataract.

PURPOSE To investigate associations between enzyme activity of glutathione reductase (GR) with and without added flavin adenine dinucleotide (FAD), glutathione peroxidase (GPX), and 6-phosphogluconic dehydrogenase (6PGDH) in the lens epithelium collected at surgery, and some nutritional and biochemical variables determined in the same individuals during the Italian-American Case-Control Study of age-related cataract. METHODS One hundred eighty-three epithelium capsule samples were collected from 174 patients undergoing surgery. Data on enzyme activity were obtained from 52 samples for 6-PGDH and from 53 samples for GR and for GPX. The Lens Opacity Classification System II was used to classify and grade cataracts. RESULTS No correlation was found between enzyme activity in lens epithelium and the same enzymatic activity in erythrocytes (with the exception of a negative correlation between lens and erythrocyte 6PGDH activity), or the type and severity of cataract. No correlation was found between lens GPX activity and plasma selenium and between lens GR activation coefficient (GRAC) and riboflavin intake. Lens GR with added FAD and lens GRAC were significantly correlated to plasma vitamin E level. Lens GRAC was positively correlated to a nutritional vitamin index. CONCLUSIONS Present data stress the difficulty in verifying the assumption that biochemical indices collected on plasma and on erythrocyte actually reflect the status of these factors in the lens itself.