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V.C. Mody, M. Kakar, A. Elfving, S. Lofgren, M. Ayala, X. Dong, U. Ungerstedt, P.G. Soderberg; Ascorbate in the Guinea Pig Lens, Dependence on Drinking Water Supplementation . Invest. Ophthalmol. Vis. Sci. 2003;44(13):3493.
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Purpose: To investigate whether lens ascorbate concentration can be elevated with drinking water supplementation in the guinea pig. Methods: Four groups of six guinea pigs ranging in weight from 304 g to 638 g received drinking water supplemented with L-ascorbate, either 0 mM, 2.84 mM, 5.68 mM, or 8.52 mM for a duration of four weeks. In addition, the chow fed to all animals contained 0.125 mol L-ascorbate/kg chow. At the end of the supplementation period, the guinea pig was sacrificed with pentobarbital overdose. Each lens was extracted, photographed, and wet weight measured. The lens was homogenized in 1.0 ml of 0.25% metaphosphoric acid, centrifuged, and supernatant ultrafiltered. The filtrate was then injected into a Polypore H HPLC column with 254 nm detection. Samples were calibrated against an L-ascorbate standard. Mean ascorbate content of the two lenses was calculated for each animal. The data were analyzed with ANOVA and multiple t-tests for unequal variances. Results: At the end of the test period, all lenses were devoid of cataract under slit lamp examination. All lenses contained a detectable concentration of ascorbate. The means and 95% confidence intervals for animal-averaged lens ascorbate concentrations (µmol/g wet weight of whole lens) per group were 0.51 +/- 0.04 [0 mM], 0.70 +/- 0.18 [2.84 mM], 0.85 +/- 0.37 [5.68 mM], and 0.71 +/- 0.06 [8.52 mM]. Welch ANOVA for unequal variances revealed a significant difference between the four groups (p<0.05). Multiple t-tests for unequal variances revealed no difference between the 2.84 mM and 5.68 mM group, no difference between 2.84 mM and 8.52 mM group, no difference between 5.68 mM and 8.52 mM group, and significant difference between 0 mM and 2.84 mM+5.68 mM+8.52 mM groups combined (p<0.05). Conclusions: The currently presented method for measurement of whole lens ascorbate content is suitable. Lens ascorbate concentration increased with drinking water supplementation in the guinea pig.
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