Oxidative defense enzyme activity and mRNA levels in lenses of diabetic rats.

Abstract

This study examines the mRNA expression and enzyme activity of oxidative defense enzymes during the course of streptozotocin-induced hyperglycemic cataract development. Diabetes was produced in 5-wk-old male Sprague-Dawley rats by administering streptozotocin ip and mRNA expression and enzyme activity were monitored on d 4, 8, 12, 16, 20, 40, 60, and 80; concomitantly, the onset and progress of cataract was followed by digital image analysis. Peak enzyme activity and mRNA expression were attained between d 20 and 40. Although catalase and glutathione peroxidase maintained high levels of mRNA expression through d 60, induction of CuZu-superoxide dismutase was transient, with the activity and mRNA levels returning to baseline values by d 40. There was a pronounced increase in aldose reductase activity, which gradually declined to basal levels by d 60; however, the mRNA levels remained unaltered. Other changes included a progressive loss of lenticular transparency, which declined to 40% of control by d 80. The role of antioxidant defense enzymes and, more interestingly, aldose reductase in combating oxidative stress in diabetic cataractogenesis is discussed.