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Results for “Dehydroascorbic Acid”

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At least 19 recordsLinked to original sources
PubMedDate not supplied

Physiological role of dehydroascorbic acid.

Dehydroascorbic acid is present in insignificant amounts in plant and animal tissue but appears in considerable amounts under various physiological and pathological conditions. It is found increased: in blood of patients suffering from infectious diseases; in blood and tissues of thyrotoxic patients; in blood after injection of thyroxin, corticotropin and cortisone. In all the above conditions there is concomitant decrease in L-ascorbic acid and glutathione values of blood and tissues. Dehydroascorbic acid, however, disappears after continued administration of a high dose of ascorbic acid. The accumulation of dehydroascorbic acid seems to be an indication of ascorbic acid deficiency. The extreme sensitivity of the ascorbate system to physiological changes is suggestive of a major biochemical role for this redox system. Accumulated evidences indicate that dehydroascorbic acid possible control cell division.

Animals↗
PubMed1991

Ascorbic acid and dehydroascorbic acid measurements in human plasma and serum.

We investigated whether circulating ascorbic acid in humans is protein bound or free and whether ascorbic acid exists in its reduced form alone as ascorbic acid or in its reduced and oxidized forms as ascorbic acid and dehydroascorbic acid, respectively. Ascorbic acid and dehydroascorbic acid were determined by using HPLC with coulometric electrochemical detection, and protein binding was determined by centrifugal ultrafiltration. Ascorbic acid was free in plasma and serum of normal, healthy volunteers, 10 men and 10 women. Ascorbic acid was detectable only in its reduced form. However, dehydroascorbic acid could be made to appear in samples processed under oxidizing conditions. Because circulating ascorbic acid is free and is detected only as reduced vitamin, ascorbic acid may be available without intermediates for peripheral utilization. Dehydroascorbic acid may not be present in plasma and serum of normal humans unless assay conditions permit ascorbic acid oxidation.

Adult↗
PubMed1991

Transport of ascorbic acid and dehydroascorbic acid by pancreatic islet cells from neonatal rats.

Several amidated biologically active peptides such as pancreastatin, thyrotropin-releasing hormone, pancreatic polypeptide and amylin are produced in endocrine pancreatic tissue which contains the enzyme necessary for their final processing, i.e. peptidylglycine alpha-amidating mono-oxygenase (EC 1.14.17.3). The enzyme needs ascorbic acid for activity as well as copper and molecular oxygen. The present work shows that pancreatic islet cells prepared from overnight cultures of isolated islets from 5-7-day-old rats accumulate 14C-labelled ascorbic acid by a Na(+)-dependent active transport mechanism which involves a saturable process (estimated Km 17.6 microM). Transport was inhibited by ouabain, phloridzin, cytochalasin B, amiloride and probenecid. Glucose inhibited or stimulated uptake, depending on the length of incubation time of the cells. The uptake of dehydroascorbic acid was linearly dependent on concentration. Dehydroascorbic acid was converted to ascorbic acid by an unknown mechanism after uptake. The uptake of both ascorbic acid and dehydroascorbic acid was inhibited by tri-iodothyronine, and uptake of ascorbic acid, but not of dehydroascorbic acid, was inhibited by glucocorticoids. Isolated secretory granules contained a fairly low concentration of iron but a high concentration of copper.

Animals↗
PubMed1975

[Simplification of the dinitrophenylhydrazine method for the photometric determination of ascorbic acid and dehydroascorbic acid in fruit juices. I. Application to juice of black current (author's transl)].

The photometric determination of ascorbic acid and dehydroascorbic acid by preparing the 2,4-dinitrophenylhydrazone derivative of dehydroascorbic acid and purifying it by thinlayerchromatography was simplified and adapted to the microliter system of Eppendorf Gerätebau, Hamburg, Germany. Using this method with juice of black current, quite reproducible results for vitamin C contents were obtained. Compared with the method of the International Federation of Fruit Juice Producers (titration with 2,6-dichlorphenolindophenol) the contents of vitamin C found with nine different commercial juices of black current were lower from 13 to 30%.

Ascorbic Acid↗
PubMed1978

Ascorbic acid and dehydroascorbic acid in HeLa cells: their effect on the collagen-peptidase activity of glucose-deficient cultures.

HeLa cells in culture do not accumulate ascorbic acid unless ascorbic acid or dehydroascorbic acid is available in the medium. Collagen peptidase corresponding to the activity found in the invasive zone of tumours, and acid phosphatase, in HeLa cells cultured under normal conditions, are unaffected by ascorbic acid, but are reduced in cells deprived of carbohydrate. These reduced collagen-peptidase levels, but not acid phosphatase, are restored to the values of normal HeLa cells by ascorbic acid. The relevance of these findings is considered in the context of tumour growth and spread.

Acid Phosphatase↗
PubMed1991

Simultaneous high-performance liquid chromatographic determination of ascorbic acid and dehydroascorbic acid in biological samples.

The ascorbic acid (AA)-dehydroascorbic acid redox couple is an important component of many biological systems, and various physiological roles have been described for this vitamin. Simultaneous measurement of both AA and dehydroascorbate using high-performance liquid chromatography (HPLC) has proven difficult owing to detection problems. A simple, single-step HPLC assay for the simultaneous detection of both AA and dehydroascorbate was developed without the burden of derivatization of either compounds. This has proven to be a reliable technique and should be applicable to a wide variety of biological samples.

Animals↗
PubMed1976

In vitro effects of ascorbic acid and dehydroascorbic acid on diphosphopyridine nucleotide diaphorase in toad testis.

The enzyme diphosphopyridine nucleotide diaphorase (DPND) was demonstrated histochemically in both the tubular and Leydig cells of the toad testis. Addition of 200 mug of dehydroascorbic acid (DHA) to 100 mg of testicular slices in the incubating medium increased the activity of DPND, while a similar dose of ascorbic acid failed to do so. The evidence indicates that DHA is involved in the oxidation of reduced DPND in toad testis.

Animals↗
PubMed1991

Ascorbic and dehydroascorbic acid measurement in human serum and plasma.

Plasma supplemented with ascorbic acid was prepared; the stability of these samples was characterized and the accuracy of the supplementation was established. Studies on the accuracy, precision, and sources of methodological bias in the measurement of ascorbic acid were summarized. Measurements of the ratio of ascorbic acid to dehydroascorbic acid in clinical samples was evaluated and was shown to be relatively constant in plasma taken from blood stored at 12 degrees C for 6 h. These results imply that whole blood has the capacity to maintain a constant ascorbic-dehydroascorbic acid ratio and suggest that this ratio may be of physiological significance.

Ascorbic Acid↗
PubMed1979

Uptake of L-ascorbic acid and L-dehydroascorbic acid by human erythrocytes and HeLa cells.

Uptake of AsA and DAsA by human cells, i.e., erythrocytes and HeLa cells, was examined in vitro. AsA was taken up very slowly, but DAsA was taken up very rapidly by erythrocytes to establish equilibrium after 1 minute. Uptake of the vitamins by HeLa cells was similar to that by erythrocytes, except there was an uptake of DAsA that reached saturation after 5 minutes. The DAsA taken up was reduced in part to AsA and the concentrations of DAsA inside and outside the cells became almost equal. GSH was responsible for this reduction. Although DAsA was evidently a more permeant form than AsA in the case of human cells, the relevance of this to the uptake of vitamin C by the tissues in vivo remains uncertain.

Ascorbic Acid↗