Effect of aging on aqueous-phase antioxidants in tissues of male Fischer rats

The purpose of this study was to determine the influence of aging on concentrations of the important aqueous-phase antioxidants in rat tissues. Ascorbic acid, glutathione and uric acid were measured in tissues and organs of male Fischer 344 rats at 6, 15 and 26 months of age. Blood, liver, lungs, heart, kidneys, brain, testes and lenses were excised rapidly and were extracted with cold metaphosphoric acid. Aging diminished the concentration of ascorbic acid in liver, lung and lens; levels in 26-month-old rats were 40-60% of those in 6-month-old rats. Glutathione content was diminished only in lens, where it decreased almost 50% between 15 and 26 months. Some age-associated increases in antioxidant levels also were seen; testis ascorbic acid and kidney glutathione levels were elevated in the old compared with the younger rats. Uric acid concentrations were much lower than glutathione or ascorbic acid concentrations in every tissue except plasma. Old rats had lower levels of uric acid in liver but higher levels in heart, kidney and testis. These results demonstrate that aqueous-phase antioxidant levels are not uniformly diminished in tissues of old rats.