Peroxide-metabolizing systems of the crystalline lens

The ability of transparent and cataractous human, rabbit and mice lenses to metabolize hydrogen peroxide in the surrounding medium was evaluated. Using a chemiluminescence method in a system of luminol-horseradish peroxidase and a photometric technique, the temperature-dependent kinetics of H2O2 decomposition by lenses were measured. The ability of opaque human lenses to catalyze the decomposition of 10(-4) M H2O2 was significantly decreased. However, this was reversed by the addition of GSH to the incubation medium. Incubation of the mice lenses with the initial concentration H2O2 10(-4) M led to partial depletion of GSH in normal and cataractous lenses. Human cataractous lenses showed decreased activities of glutathione reductase, glutathione peroxidase (catalyzing reduction of organic hydroperoxides including hydroperoxides of lipids), superoxide dismutase, but no signs of depletion in activities of catalase or glutathione peroxidase (utilizing H2O2). The findings indicated an impairment in peroxide metabolism of the mature cataractous lenses compared to normal lenses to be resulted from a deficiency of GSH. An oxidative stress induced by accumulation of lipid peroxidation products in the lens membranes during cataract progression could be considered as a primary cause of GSH deficiency and disturbance of the redox balance in the lens.