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Biomedical subjects

D Hornig

Publications and source records attributed to D Hornig.

At least 37 records · Page 2Linked to original sources
PubMed1977

Interaction of erythorbic acid with ascorbic acid catabolism.

There exist altogether four stereoisomers of ascorbic acid. Erythorbic acid (D-isoascorbic acid) differs in the spatial configuration at carbon 5 and has less than 5 per cent of biological vitamin C activity. In guinea pigs, depending on an exogenous supply of ascorbic acid, a possible interaction of erythorbic acid with absorption, transport through the cell membranes at the tissue level, or with catabolism of ascorbic acid has been investigated. After oral administration, results suggest no difference in absorption of these two compounds from the intestine, whereas uptake by the tissues was approximately four to one in favour of ascorbic acid. Feeding experiments with erythorbic acid indicate the availability of ascorbic acid being diminished by 40-60% when administered together with erythorbic acid. Kinetic data on the catabolism of ascorbic acid showed a significant reduction in half-life (50% of the dose excreted) of the vitamin caused by administration of erythorbic acid. The results suggest the oxidative destruction of ascorbic acid in the liver being significantly accelerated. Thus, ingestion of erythorbic acid interacts with newly introduced ascorbic acid by enforcing the breakdown of ascorbic acid. Implications of these findings for the metabolism, availability and nutritional status of ascorbic acid in humans will be discussed.

Animals↗
PubMed1977

On the absorption of ascorbic acid in man.

The daily intake of ascorbic acid with the diet was strongly restricted in seven healthy non-smoking males and 90 to 180 mg of ascorbic acid were orally supplemented. After an equilibration period of three weeks about 5 muCi of (1-14C) ascorbic acid was orally administered with carrier (30 mg or 60 mg). The daily intake was then increased to 4 X 1000 mg and the cumulative excretion of radioactivity in the urine measured over a period of 10 days. The average absorption was estimated to amount to 80-90% of the dose.

Administration, Oral↗
PubMed1976

Ascorbic acid and cholesterol: effect of graded oral intakes on cholesterol conversion to bile acids in guinea-pigs.

A significant correlation between liver ascorbic acid (AA) and total bile acids or liver bile acids has been established in guinea-pigs by direct determination of the bile acids, confirming an earlier hypothesis. The oxidation of cholesterol to bile acids is dependent on the AA status, but it cannot be further stimulated by AA when the animals are already on an adequate intake of the vitamin. This suggests that AA has a hypocholesterolaemic effect over a limited range of AA status.

Animals↗
PubMed1976

Interaction of erythorbic acid with ascorbic acid catabolism.

After a vitamin C depletion period of 12 days supplementing erythorbic acid (50 mg/day/kg bodyweight) over 16 days significantly accelerated the catabolism of a newly ingested tracer dose of (1-14C) ascorbic aicd in guinea pigs in comparison to animals supplemented with ascorbic acid (5 mg/day/kg bodyweight), but this effect of erythorbic acid could not be normalized by additional supplementation with ascorbic acid. Half-lives for (1-14C) ascorbic acid (50% of the dose excreted) were drastically reduced from 97 h to 50 h and 59 h, respectively. Also figures on the retention of radioactivity showed the availability of ascorbic acid to be reduced. This is in accordance with the significant reduction in size of ascorbic acid bodypool, and in weight gain in the groups receiving erythorbic acid, or erythorbic and ascorbic acids. The bioavailability was calculated to be strongly depressed to nearly 50% of the total ingested biologically active material (ascorbic plus erythorbic acids), assuming erythorbic acid to have only one-twentieth of the biological activity of ascorbic acid.

Animals↗
PubMed1975

Cerebral monoamine metabolism in guinea-pigs with ascorbic acid deficiency.

Guinea-pigs kept on a diet deficient in vitamin C showed, after 3 weeks, a marked decrease of ascorbic acid in brain and blood leucocytes as well as of the activity of alkaline phosphatase in blood plasma. Pair-fed animals did not exhibit these changes. The alpha-methyl-p-tyrosine (alpha MpT)-induced diminution of noradrenaline in the hypothalamus and the rest of the brain was attenuated in pair-fed animals, but restored in guinea-pigs deficient in ascorbic acid. The cerebral noradrenaline content (without administration of alpha MpT) showed a decrease in both pair-fed and ascorbic acid deficient animals. The noradrenaline of the heart exhibited a similar tendency. The alpha MpT-induced dopamine decrease in the striatum of ascorbic acid deficient animals was attenuated and the dopamine content (without alpha MpT administration) decreased. Pair-fed animals showed a similar tendency. The striatal concentration of homovanillic acid (HVA) was diminished in both pair-fed and ascorbic acid deficient guinea-pigs. The cerebral content of 5-hydroxyindoleacetic acid showed a decrease in pair-fed as well as in ascorbic acid deficient animals. It is concluded that ascorbic acid deficiency enhances the turnover of brain noradrenaline, whereas under-nutrition without ascorbic acid deficiency (pair-feeding) diminishes the turnover of cerebral noradrenaline, 5-hydroxytryptamine and striatal dopamine.

Alkaline Phosphatase↗