| Popis: |
The effect of ascorbic acid intake on tissue levels of ascorbic acid, dehydroascorbic acid and the ratio of dehydroascorbic acid to ascorbic acid in mice was studied. In general, the trend of changes in tissue concentrations was: ascorbic acid > dehydroascorbic acid ≫ ratio of dehydroascorbic acid to ascorbic acid. Mice fed a diet with 1% ascorbic acid had significantly higher concentration of dehydroascorbic acid in the kidney, lung and spleen than did control mice fed an ascorbic acid-free diet. Mice fed a diet with 5% ascorbic acid had elevated levels of dehydroascorbic acid in the brain, kidney, liver, lung and spleen. The kidney and lung had the greatest increase in dehydroascorbic acid concentration, suggesting that these two organs may be important sites for catabolism and elimination of ascorbic acid. In comparison with the corresponding control values, the ratio of dehydroascorbic acid to ascorbic acid was higher in the lung, not different in the liver and spleen, and lower in the kidney of mice fed a diet with 1 or 5% added ascorbic acid. These ratios were higher in the brain of mice fed a diet with 5% added ascorbic acid than in mice fed the ascorbic-acid-free diet. No apparent physiological abnormality in these animals was observed. These effects were stereospecific. Exogenous erythorbic acid, D-isoascorbic acid, a stereoisomer of ascorbic acid, increased dehydroascorbic acid equivalents (the sum of dehydroascorbic and dehydroerythorbic acid) in the kidney, lung, and spleen but the ratios of dehydroascorbic acid plus dehydroerythorbic acid to ascorbic acid plus erythorbic acid were essentially unaffected. A large glucose intake (1 or 5% in the diet) did not have an effect on levels of tissue ascorbic acid or dehydroascorbic acid. |
