Ascorbate Effect on Development of Ultraviolet Radiation–B(UVR–B)–Induced Cataract in Cultured Rat Lenses

Abstract

Purpose: : To investigate loading of ascorbate into lenses in vitro and to study whether ascorbate protects against UVR–B–induced cataract in vitro.

Methods: : Part #1: Six Sprague–Dawley rats were sacrificed and lenses extracted. Lenses were incubated for 5 hours in culture medium with 0 mM or 4 mM ascorbate. Thereafter, each lens was processed and HPLC with ultraviolet detection was used for ascorbate measurement. Part #2: Ten Sprague–Dawley rats were sacrificed and lenses extracted. Lenses were incubated for 5 hours in culture medium with 0 mM or 4 mM ascorbate. Both lenses from each animal were exposed to 2.0 kJ/m2 UVR–B (302 nm) and cultured. On day 1, 3, 5, and 7 after exposure, lens forward light scattering was measured.

Results: : Part #1: Lens ascorbate concentrations expressed as 95% confidence intervals for the means (micromol/g wet weight lens) were 0.208 ± 0.019 [0 mM ascorbate] and 0.903 ± 0.069 [4 mM ascorbate]. Part #2: UVR–B exposed lenses developed severe cortical cataract. 95% confidence intervals for the mean of forward light scattering (tEDC) for the lenses incubated with 0 mM ascorbate for the post–UVR–B exposure time points were: 0.067 ± 0.013 [1 day]; 0.168 ± 0.023 [3 days]; 0.429 ± 0.067 [5 days]; 0.473 ± 0.022 [7 days]. For the lenses incubated with 4 mM ascorbate, the measurements were: 0.062 ± 0.015 [1 day]; 0.158 ± 0.021 [3 days]; 0.455 ± 0.083 [5 days]; 0.475 ± 0.034 [7 days].

Conclusions: : Ascorbate loading in culture medium for 5 hours in vitro increased lens ascorbate concentration in the rat four fold. Increased ascorbate content in the rat lens did not protect against UVR–B–induced cortical cataract in vitro.

Keywords: radiation damage: light/UV • antioxidants • oxidation/oxidative or free radical damage