Dose-Response Relationship for A-Tocopherol Prevention of Ultraviolet Radiation Induced Cataract in Rats

Abstract

Purpose:: To investigate if the preventive effect of α-tocopherol on ultraviolet radiation (UVR) induced cataract in an in vivo animal model is dose-dependent.

Methods:: Five groups of twenty, six-week-old female albino Sprague Dawley rats were used in present study. One group without any α- tocopherol feeding was the control group, while the other four groups received 5, 25, 50, and 100 IU/day of α- tocopherol by oral administration respectively. After 4 weeks of feeding, each rat was unilaterally exposed 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 photographed, and forward light scattering was measured.

Results:: The UVR-exposed lenses in the α-tocopherol fed groups developed superficial and slight equatorial cataract, whereas lenses in the control group developed cortical and dense equatorial opacities. Forward light scattering in lenses from the α-tocopherol-supplemented rats was lower than in lenses from the control group. Lenses in rats that had been fed 25 IU/day of α-tocopherol expressed the lowest intensity of forward light scattering. Lenses in rats that had been fed 50 or 100 IU/day expressed no significant difference in forward light scattering than lenses from rats that had been fed 25 IU/day. There was no difference in lens opacity or forward light scattering among non-exposed lenses.

Conclusions:: Oral administration of α-tocopherol to rat protects the lens against UVR-induced cataract. The protection is dose dependent and saturable.

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