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Biomedical subjects

J E Halver

Publications and source records attributed to J E Halver.

15 recordsLinked to original sources

Separation of three commercial forms of vitamin C (ascorbic acid, ascorbic-2-sulfate and ascorbate-2-polyphosphate) by HPLC.

A modification of an existing separation technique by this laboratory is described for the separation and quantification of the three commercially available forms of ascorbic acid. The technique has the potential for identifying the various metabolic and degradation products resulting from vitamins C2 and C3 metabolism. A microwave technique is used for tissue heat denaturation and extraction.

Animals

Brain ascorbate depletion as a response to stress.

Ascorbate-depleted rainbow trout were fed a single dose of L-1-14C-ascorbic acid, then held in metabolism chambers for four consecutive five-day periods. Tissue samples were analyzed for 14C, ascorbate, and ascorbate-2-sulfate. Brain ascorbate showed a long turnover time following a very slow uptake. The loss of brain ascorbate after five days in metabolism chambers was highly significant (p less than 0.001) when compared with similar dosed fish not chambered. A brain ascorbate pool which does not exchange with the body pool is proposed. Possible mechanisms are discussed and a kinetic model is suggested.

Animals

Metabolism of ascorbic acid and ascorbic-2-sulfate in man and the subhuman primate.

Man does not catabolize ascorbate to CO2, whereas the monkey does catabolize ascorbate and ascorbate sulfate to CO2 when these compounds are given orally. However, it takes the same length of time to produce frank scurvy in both man and the monkey, thus indicating that the comparative storage, rate of use, and mode of metabolism of ascorbate is similar in both species. Preliminary feeding and isotope studies conducted on monkeys are in agreement with the fact that only a small amount of labeled ascorbate or ascorbate sulfate equilibrated with body stores. These results are in agreement with published ascorbic acid requirements of 10 mg/kg body weight. In our experiments, 250 mg/day had to be fed to a 10-kg monkey to completely clear all signs of scurvy and return blood ascorbate levels to normal. Ascorbic acid administered intravenously to monkeys appears to equilibrate completely with the ascorbate pool(s). Ascorbate sulfate was found to be a urinary metabolite of both ascorbic-1-14C acid and ascorbic-6-14C acid fed orally to monkeys.

Animals