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M.F. Lou, K. Xing; Effect of Age on Glutathione and Thioredoxin Systems in the Human Lens . Invest. Ophthalmol. Vis. Sci. 2006;47(13):3520.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate the effect of age on the key oxidation repair enzyme systems of glutathione (GSH)/thioltransferase (TTase)/glutathione reductase (GR) and NADPH/thioredoxin (TRx)/thioredoxin reductase (TR) in the human lens.
23 normal human lenses ranged from 19–77 were divided into groups by decades (number of lenses) in the following: 2nd (2), 3rd (3), 5th (7), 6th (6) and 7th (5), and used for the analysis of enzyme activities. GSH–dependent TTase was assayed using HEDS as substrate in the presence of GSH, GR and NADPH; NADPH–dependent TRx was assayed using insulin as the substrate in the presence of TR and NADPH; TR activity was measured using DTNB as the substrate. Analysis of Glyceraldehyde 3–phosphate dehydrogenase (G3PD) and GR were using conventional methods while GSH was quantified using DTNB microanalysis.
TTase activity showed little change during the age span of these five groups but GR was progressively lost as a function of age. The GR activity at the 2nd–3rd decade groups was 1800 mU/g wet wt compared with 1300 mU/g wet wt in the 7th decade group. TRx activity changed insignificantly with age but the activity of TR was significantly lost with age. The younger groups showed TR activity of 220 mU/g wet wt but only140 mU/g wet wt remained in the 7th decade group. In contrast, the activity of G3PD showed extensive suppression with age, and the activity was <50% after 60 yrs of age in comparison with age in the 20–30 yr–old group. In these lens tissues, the levels of GSH were gradually depleted in the lenses with older age, in which about 40% GSH remained compared with the younger lenses.
Age showed little effect to the oxidation–resistant TTase and TRx, but the lowered activity in the respective reductase, GR and TR, and the smaller size of GSH pool may lead to redox imbalance, which may contribute to a higher risk to cataract formation in the aging lenses.
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