Spleen ascorbic acid levels

The adrenal glands and pituitary glands have the highest tissue concentration of ascorbic acid. The brain, Hver, and spleen, however, represent the largest contribution to the body pool. Plasma and leukocyte ascorbic acid levels decrease with increasing age (152). Elderly people require higher ascorbic acid intakes than children to reach the same plasma and tissue concentration (153). 

Biochemical changes in scurvy not associated with discrete enzymes have been reported. The ratio of RNA to DNA increased in spleen and adrenals (G6). The DNA content of a fibrosarcoma was decreased by scurvy, and glucoascorbic acid given to lower the tissue ascorbic acid levels in rats decreased the DNA in rat carcinoma (S21). Dinning et al. (D15) expected defects in the reactions where folic acid participates. 

Intestinal absorption of is low, ranging from 0.4% to 2.5%, so fecal output is mainly unabsorbed dietary chromium. Absorption is increased marginally by ascorbic acid, amino adds, oxalate, and other dietary factors. After absorption, chromium binds to plasma transferrin with an affinity similar to that of iron. It then concentrates in human liver, spleen, other soft tissue, and bone. Urine chromium output is around 0.2 to 0.3 U,g/day, the amount excreted being to some extent dependent upon intake. Paradoxically, urine output appears to be relatively increased at low dietary levels. Thus 2% is lost in urine at an intake of lOpg/day, but only 0.5% at an intake of 40pg/day. Both running and resistive exercise increases urine chromium excretion. 

Extensive research has been conducted in guinea pigs whereby relationships between ascorbic acid and iron were studied. Alterations in spleen and hepatic iron levels of hemosiderin and ferritin as well as changes in hepatic microsomal cytochrome P-450 have been observed with ascorbic acid deficiency (27-29). 

The relationship of the above observations in ascorbate-deprived guinea pigs to lymphocyte dysfunction is not clear-cut. Observations by Fraser et al. (1978) on lymphocytes from scorbutic animals suggested a decrease in T lymphocyte count and an increase in B lymphocytes. This phenomenon was reversed when animals were supplemented with a high dose (250 mg/day) of ascorbate. The scorbutic animals had a lower T cell response to concanavalin A (Con A) and an increased B cell response to lipopolysaccharide, compared to animals on diets replenished with ascorbic acid. However, Anthony et al. (1979) did not observe a reduction in T cells in the spleen of scorbutic animals. Because vitamin C-deficient diets can lead to inanition and scorbutic animals are more susceptible to infections, better models are needed to address the relationship between direct effects of vitamin C level and lymphocytic function (Cunningham-Rundles et al., 1993). 

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