Effect of Ultraviolet Radiation–B (UVR–B) Exposure on Lens Ascorbate Concentration in the Pigmented Guinea Pig

Abstract

Purpose: : To investigate the effect of ultraviolet radiation–B (UVR–B) exposure on lens ascorbate concentration in the pigmented guinea pig.

Methods: : Twenty 20 pigmented guinea pigs were randomly divided into two groups. One group received drinking water supplemented with 0 mM ascorbate while the other group received drinking water supplemented with 5.5 mM ascorbate, for four weeks. All animals were thereafter unilaterally exposed to UVR–B. One day after the exposure to UVR, the animals were sacrificed and the lenses were removed for measurement of intensity of forward light scattering. Ascorbate concentration was measured once in each lens using ultrafiltration and HPLC with UVR detection.

Results: : There was no significant difference of ascorbate content between exposed and not exposed lenses in either of the 0 mM or the 5.5 mM group [t–test]. Anterior subcapsular cataract developed in all exposed lenses and none of not UVR–exposed lenses. In both the ascorbate–supplemented and the not supplemented group, the lens light scattering was significantly higher in UVR–B–exposed lenses than in the not exposed lenses. A 95 % confidence interval for the mean difference beween exposed and contralateral not exposed lens was 0.036 ±0.014 tEDC for ascorbate–supplemented animals and 0.039 ±0.014 tEDC for non–supplemented animals.

Conclusions: : UVR–B exposure causes cataract but does not induce a decrease in lens ascorbate concentration in exposed versus non–exposed lenses in the pigmented guinea pig, regardless of ascorbate supplementation or not. The ascorbate finding is in contrast to that for a similar experiment in the rat, which may be explained by the higher ocular ascorbate levels in the guinea pig.

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