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Lisa M. Bova, Matthew H. J. Sweeney, Joanne F. Jamie, Roger J. W. Truscott; Major Changes in Human Ocular UV Protection with Age. Invest. Ophthalmol. Vis. Sci. 2001;42(1):200-205. doi: https://doi.org/.
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purpose. Age-dependent human lens coloration may be explained by the binding of
UV filters to crystallins. It has been proposed that glutathione may
compete for reaction with UV filter degradation products and therefore
protect crystallins from modification. To understand this process, UV
filters were quantified together with oxidized and reduced glutathione
in human lenses of varying age.
methods. Lens tissues were homogenized in ethanol to extract the UV filters.
Metabolites were quantified by HPLC and correlations between them in
the nuclear and cortical regions of the lens were examined.
results. The concentrations of the UV filters 3-hydroxykynurenine,
kynurenine, and 3-hydroxykynurenine glucoside decreased linearly with
age, with slightly lower levels in the nucleus than the cortex.
4-(2-Amino-3-hydroxyphenyl)-4-oxobutanoic acid glucoside was found
in higher levels in the nucleus than the cortex and decreased slowly in
both regions with age. Glutathionyl-3-hydroxykynurenine glucoside was
present in higher concentrations in the nucleus, barely detectable in
young lenses, but increased significantly after age 50. Reduced
glutathione levels were lower in the nucleus and decreased in both
regions with age, yet oxidized glutathione increased in the nucleus but
remained constant in the cortex.
conclusions. Results are consistent with a predominantly nuclear origin for both
4-(2-amino-3-hydroxyphenyl)-4-oxobutanoic acid glucoside and
glutathionyl-3-hydroxykynurenine glucoside. This is in accord with
their proposed mechanism of formation, which involves an initial
deamination of 3-hydroxykynurenine glucoside. This process is more
pronounced in older lenses, possibly because of the barrier to
diffusion. The barrier may also explain the increase in nuclear
oxidized glutathione that is observed with age.
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