Redox Balance in the Lens After in vivo Exposure to UVR, Dependence of Alpha-Tocopherol Supplementation

Abstract

Purpose: : To investigate the redox balance in the albino rat lens as a function of dose of oral supplementation of alpha-tocopherol dose after in vivo exposure to ultraviolet radiation (UVR).

Methods: : Five groups of twenty, six-week-old female albino Sprague Dawley rats were for four weeks supplemented with 0, 5, 25, 50, and 100 IU/day alpha-tocopherol orally depending on group belonging. Then, each rat was unilaterally exposed in vivo to 8 kJ/m² (exp time 15 min ) UVR-300 nm. The rats were sacrificed at 1 week after exposure to UVR and 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: : UVR induced light scattering was dose dependently protected with Alpha-tocopherol with a rate constant (1/e) of 4.8 IU/day. UVR exposure cased a depletion of total lens GSH at low alpha-tocopherol supplementation that recovered towards higher alpha-tocopherol supplementation but did not cause any alteration of total lens GSSG at any level of alpha-tocopherol supplementation. No alteration of total lens GR- or GPx activity at any level of alpha-tocopherol supplementation was observed after UVR exposure.

Conclusions: : Alpha-tocopherol protects against UVR induced light scattering, dose dependently. The protection is associated with a reduction of GSH depletion caused by UVR exposure without any effect on total lens GSSG or GR- or GPx activity.

Keywords: radiation damage: light/UV • cataract • antioxidants