Antioxidant enzymes in the human iris: an immunogold study

AIMS To determine the nature and extent of the antioxidant enzyme system in the human iris. METHODS The fine structural distribution of five antioxidant enzymes (acidic, neutral, and basic glutathione S-transferase (GST), Cu/Zn superoxide dismutase (Cu/Zn SOD), and glutathione peroxidase) was determined by immunogold labelling of ultrathin sections of tissue from six eyes appropriately fixed for immunocytochemistry and embedded in LR white resin. RESULTS Both Cu/Zn SOD and acidic GST were localised to all constituent cells of the iris. Glutathione peroxidase and basic GST were localised to erythrocytes alone, and labelling for neutral GST was absent. CONCLUSIONS Dense labelling for acidic GST could be linked with the previously documented presence of large quantities of polyunsaturated fatty acids in the iris and/or the presence of xenobiotic substances in the aqueous humour.