Dose dependence of alpha-tocopherol protection against in vivo ultraviolet radiation and associated alterations in lens redox balance

Purpose: To investigate the dose dependence of alpha-tocopherol protection against in vivo ultraviolet radiation (UVR) induced light scattering and associated alterations in the redox balanced in the albino rat lens. Methods: Five groups of twenty, six-week-old female albino Sprague Dawley rats were supplemented with 0, 5, 25, 50, and 100 IU/day alpha-tocopherol orally depending on group belonging for 4 weeks. Then, each rat was unilaterally exposed in vivo to 8 kJ/m2 UVR-300 nm for 15 min. At 1 week after exposure to UVR, the rats were sacrificed, the lenses were extracted and homogenized. Lens total reduced (GSH) and oxidized (GSSG) glutathione; glutathione- reductase (GR) and oxidase (GPx) were determined colorimetrically by enzyme reactions. Results: Alpha-tocopherol caused a dose-dependent protection against UVR induced light scattering with a rate constant (1/e) of 4.8 IU/day. The exposure to UVR caused a depletion of total lens GSH at low alpha-tocopherol supplementation that recovered towards higher alpha-tocopherol supplementation. The UVR exposure did not cause any alteration of total lens GSSG at any level of alpha-tocopherol supplementation. The UVR exposure did not cause any alteration of total lens GR- or GPx activity at any level of alpha-tocopherol supplementation. Conclusions: Alpha-tocopherol dose dependently protects against UVR induced light scattering. The protection of UVR induced light scattering is associated with a reduction of GSH depletion due to UVR exposure without any effect on total lens GSSG or GR- or GPx activity