Dose-response relationship for alpha-tocopherol prevention of ultraviolet radiation induced cataract in rat

• The purpose of this study is to establish the dose response relationship for alpha-tocopherol protection of ultraviolet radiation (UVR) induced cataract in the rat. Four groups of 20 six-week-old albino Sprague Dawley rats received 5, 25, 50, and 100 IU/day alpha-tocopherol, whilst another group of 20 rats without any alpha-tocopherol feeding was the control group. After 4 weeks of feeding, each rat was unilaterally exposed to 8 kJ/m(2) UVR-300 nm for 15 min. At 1 week after exposure, the rats were sacrificed and lens light scattering was measured quantitatively. Lens total reduced (GSH) and oxidized (GSSG) glutathione; glutathione reductase (GR) and peroxidase (GPx) were determined spectrophotometrically. The UVR-exposed lenses in the alpha-tocopherol fed groups developed superficial cataract, whereas lenses in the control group developed cortical and equatorial opacities. Light scattering in lenses from the alpha-tocopherol-supplemented rats was lower than in lenses from the control group. The difference of light scattering between the exposed and contralateral non-exposed lens decreased with increasing doses of alpha-tocopherol to an asymptote level. UVR-exposure caused a significant depletion of lens GSH in rats without or at low alpha-tocopherol supplementation. The depletion of GSH became less with higher alpha-tocopherol supplementation. There was no detectable difference in lens GSSG, GR or GPx at any level of alpha-tocopherol supplementation. Orally administered alpha-tocopherol dose dependently protects against UVR-induced cataract. The protection is associated with an alpha-tocopherol dose-dependent GSH depletion secondary to UVR exposure. UVR-induced light scattering only occurs if the GSH depletion exceeds a threshold.

Ämnesord

MEDICIN OCH HÄLSOVETENSKAP  -- Klinisk medicin -- Oftalmologi (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Clinical Medicine -- Ophthalmology (hsv//eng)

Nyckelord

forward light scattering

lens

cataract

ultraviolet radiation

alpha-tocopherol

dose-dependent

Ophtalmiatrics

Oftalmiatrik

Publikations- och innehållstyp

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