In vivo quantitative measurement of antioxidant effects in the lens

Abstract

AbstractTo evaluate the protective effect of antioxidants on experimental cataract induced by ultraviolet radiation (UVR). The protective effect of the antioxidants alpha‐tocopherol and caffeine and the antioxidant gene Grx‐1 were investigated. For investigation of the antioxidants, albino Sprague Dawley rats were used and for the Grx‐1 gene, a Grx‐1 knockout C57BL/6 mouse and its inbred wild type were used. As an oxidation insult, all animals were exposed to around threshold dose UVR in the 300 nm wavelength region, delivered during 15 min. The UVR was generated with a high pressure mercury arc lamp and the waveband was limited to around 300 nm. Dosimetry was assured with a calibrated thermopile. The rats and mice were sacrificed at 1 week and 48 hrs after exposure, respectively. Then, the lenses were extracted for forward light scattering measurement. In all three experiments, the animals were grouped at five different dose levels centered around the expected threshold dose. The Maximum Tolerable Dose‐2.3;16 (MTD‐2.3;16) was used as threshold estimate. The protection factor (PF) was calculated as the ratio between the threshold dose with protective factor and the threshold without the protective factor. The threshold dose for alpha‐tocopherol was with and without 3.0 and 2.7 kJ/m^2, respectively (PF= 1.1). The threshold dose for caffeine was with and without 5.7 and 4.6 kJ/m^2, respectively (PF= 1.2). The threshold dose for Grx‐1 was with and without 3.8 and 3.0 kJ/m^2, respectively (PF= 1.3). As measured in vivo, caffeine has a more potent antioxidant effect after topical application than alpha‐tocopherol administered parenterally. The Grx‐1 gene provides the most potent antioxidant effect in vivo.