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PubMedDate not supplied

Ascorbic acid supplementation and copper status in rats.

The effect of a high concentration (1%, w/w) of ascorbic acid in a Cu-adequate (150 mumol/kg) purified diet was studied in rats. After 6 wk, ascorbic acid had significantly reduced Cu concentrations in muscle and bone. The estimated whole body content of Cu in rats fed ascorbic acid was reduced by 20%. Within 1 d after oral administration of 64Cu, the recovery of the dose in feces was increased in rats fed ascorbic acid, suggesting that the vitamin depresses intestinal absorption of Cu. After intraperitoneal (ip) administration of 64Cu, the rate of loss of the dose from the body was decreased in rats fed ascorbic acid. This study suggests that the ascorbic acid induces a decreased efficiency of intestinal Cu absorption, which in turn triggers mechanisms to preserve Cu in the body stores. This is supported by the observation that the feeding of a Cu-deficient diet (5 mumol/kg) had similar effects, although more pronounced.

Animals↗
PubMed1981

Effect of large oral doses of ascorbic acid on uric acid excretion by normal subjects.

The effects of large and oral doses of ascorbic acid on renal clearance and excretion of uric acid were studied in nongouty subjects because ascorbic acid has been reported to increase renal uric acid clearance. Our results indicate that 4 or 12 gm ascorbic acid taken in divided doses had no effect on serum uric acid concentration or uric acid excretion and clearance by the kidney. Reasons for these results, which differ from previous reports, are discussed. We quantitated the magnitude of the interference of ascorbic acid in the measurement of uric acid by the nonspecific methods frequently used, since falsely elevated urine uric acid could lead to misinterpretation of screening tests.

Administration, Oral↗
PubMed1989

Anion-exchange high-performance liquid chromatographic determination of ascorbic acid and hexavalent chromium in rat lung preparations after treatment with sodium chromate in vitro and in vivo.

Simultaneous analysis of ascorbic acid and chromium (VI) in soluble fractions and bronchoalveolar lavage fluids of rat lungs treated with sodium chromate in vitro and in vivo was performed by anion-exchange high-performance liquid chromatography coupled to a photodiode-array detector. Absorbances at 265 and 370 nm were used for the determination of ascorbic acid and chromium (VI), respectively. The calibration graphs of standard solutions were linear in the test ranges of ascorbic acid an chromium (VI) (below 10 and 8 ppm, respectively). The detection limits of ascorbic acid and chromium (VI) were 1 and 0.5 ng, respectively. The recovery of ascorbic acid from lung tissues homogenized at pH 7.4 was 99%, and that of chromium (VI) was 96%, when tissues were homogenized under alkaline conditions (pH 11.4). Using this method, ascorbic acid levels in the soluble fractions and lavage fluids of normal rat lungs were determined. In the lung of a rat intratracheally injected with a saline solution of sodium chromate, ascorbic acid decreased to 80% of the normal level, and ca. 90% of the chromium (VI) was reduced within 4 min after injection, indicating that the ascorbic acid-related reduction of chromium (VI) is very rapid. The present method will be useful for studies of the reduction of chromium (VI) by ascorbic acid in biological systems.

Animals↗
PubMed2002

Influence of time period of cadmium intoxication on the concentrations of ascorbic acid selenium in certain tissues and blood serum of rats.

Ascorbic acid and selenium are important antioxidants for the reactive forms of oxygen. The purpose of these experiments was to determine the influence of various concentrations of cadmium on ascorbic acid and selenium concentrations in certain tissues of rats. The results showed that cadmium, added to rats' feed, influenced the concentration of ascorbic acid in blood serum and tested rats' tissues. Cadmium influenced the concentration of selenium in certain tissues as well. Furthermore, it has been demonstrated that ascorbic acid and selenium concentrations are dependent on the type of tissue tested as well as on the size of cadmium concentrations and length of the experiments.

Animals↗
PubMed1982

Effects of ascorbic acid on the uptake of serotonin in differentiated neuroblastoma cells.

Ascorbic acid causes concentration-dependent and time-dependent effects on [3H]-serotonin (3H-5HT) uptake into differentiated neuroblastoma N-2a cells. Preincubation of cells with ascorbic acid inhibits both passive diffusion and active transport of 3H-5HT (0.1 microM). The kinetic characteristics of the active uptake process change with ascorbic acid treatment, resulting in an increase in the Km from 0.27 microM to 3.0 microM and in the Vmax from 453 to 2369 fmol/min/10(6) cells. This inhibitory effect of ascorbic acid appears to be due to its reducing properties.

Animals↗
PubMed1981

Effect of ascorbic acid and ferrous iron on p-aminohippurate accumulation by rat kidney cortical slices.

The effect of ascorbic acid and Fe2+ on p-aminohippurate accumulation by rat kidney slices was examined. Ascorbic acid and Fe2+ promoted lipid peroxidation of rat renal cortical slices was found to be dose related. Moreover, ascorbic acid (1.0 mM) and Fe2+ (0.4 mM) increased tissue water and decreased the accumulation of p-aminohippurate. The addition of N,N'-diphenyl-p-phenylenediamine (antioxidant) at the concentration of 1 x 10(-6) M recovered the accumulation of p-aminohippurate by about 43%. The apparent Km of p-aminohippurate uptake was increased by ascorbic acid and Fe2+ with no change in the apparent V. These data suggest that ascorbic acid and Fe2+ can cause a significant alteration in p-aminohippurate and water transport of renal cortical slices and that these effects may be, at least, partly due to the lipid peroxidative action of ascorbic acid and Fe2+.

Aminohippuric Acids↗
PubMed1995

A model study on rate of degradation of L-ascorbic acid during processing using home-produced juice concentrates.

The rate of degradation of L-ascorbic acid in solution has been investigated under varying conditions, such as temperature, level of dissolved oxygen, pH, amino acids, sugars and processing conditions. Changes in pH between pH 1.5 and 7.0 accelerate L-ascorbic acid degradation. The most important factor that determines its stability is storage temperature, on which the rate of degradation of L-ascorbic acid is directly dependent. Similarly, the deleterious effect of variables such as oxygen and pH are influenced by temperature. Therefore, low temperature storage is imperative in order to regard L-ascorbic acid delay. A definite role of amino acids in L-ascorbic acid degradation has not been identified.

Amino Acids↗
PubMed1987

Flavin-containing monooxygenase and ascorbic acid deficiency. Qualitative and quantitative differences.

Ascorbic acid deficiency causes qualitative and quantitative differences in the guinea pig hepatic flavin-containing monooxygenase (FMO). Kinetic studies with purified FMO indicated no significant change in the apparent Km of dimethylaniline or NADPH in ascorbate-supplemented or -deficient animals. Following purification of ascorbate-deficient guinea pig FMO by DEAE-cellulose and blue agarose chromatography, exogenous FAD was required for 15% of the FMO microsomal activity recovered. In contrast, only 5% of the total microsomal enzyme recovered from ascorbate-supplemented animals required exogenous FAD. Furthermore, there was an enhanced sensitivity to time-dependent nonlinearity with the purified ascorbate-deficient guinea pig FMO. The degree of time-dependent nonlinearity was related to the concentration of substrate. Also, purified ascorbate-supplemented guinea pig FMO was stable for 4 weeks at -20 degrees, whereas the ascorbate-deficient enzyme was inactivated. A decrease in the quantity of ascorbate-deficient guinea pig FMO compared to ascorbate-supplemented was indicated by a marked reduction in total FMO activity recovered from blue agarose chromatography and reduced protein staining intensity with SDS-PAGE at 56,000 daltons.

Animals↗
PubMed1986

Onset and growth rate of solid tumours derived from implanted ascites tumour cells pretreated with ascorbic acid.

A study on the onset and growth kinetics of solid tumours obtained by injecting ATP C+ cells preincubated with ascorbic acid, iodoacetate or citric acid into BALB Cf/Had/Se substrain mice showed that ascorbic acid was not as effective as iodoacetate in inhibiting the growth of these tumours, since higher doses of ascorbic acid were required to obtain a similar effect. This suggests that ascorbic acid, unlike iodoacetate, does not act by blocking the SH groups. Furthermore, not only did incubation of ATP C+ cells with lower doses of ascorbic acid fail to inhibit tumour growth, but rather favoured the growth of solid tumours derived from these cells. Other experiments designed to evaluate the degree of immunity provided by ascorbic acid, iodoacetate and citric acid pretreated cells in mice indicated that such treatment was of limited efficiency, since it considerably reduced the antigenicity of the cells.

Animals↗
PubMedDate not supplied

Dental chairside test for the diagnosis of ascorbic acid deficiency.

There is a strong correlation between gingival inflammation and clinical and sub-clinical ascorbic acid deficiency. This has created a demand for a handy diagnostic test to detect the ascorbic acid deficiency. The aim of this work was to find out the efficacy of one such test, i.e. the modified Lingual Ascorbic Acid Test (LAAT). To find out the significance of ths LAAT, it was compared with plasma ascorbic acid levels and then confirmed statistically. Our findings suggest that with this simple, reliable and inexpensive method, the dental practitioners can conveniently assess the ascorbic acid status of their patients.

2,6-Dichloroindophenol↗
PubMed2003

Differential distribution of ascorbic acid, peroxidase activity, and hydrogen peroxide along the root axis in Allium cepa L. and its possible relationship with cell growth and differentiation.

In this paper we show an asymmetrical distribution of apoplastic and symplastic ascorbic acid content, peroxidase activities and hydrogen peroxide along the root axis in Allium cepa L. For most of these metabolites, a marked gradient from the root apex to the onion base was observed and was different for apoplastic and symplastic compartments. In total homogenates, ascorbic acid content was higher in the zones closer to the apex and decreased towards the root base. However, an opposite pattern was observed in the apoplastic fraction. Peroxidase activities with guaiacol, ferulic acid, ascorbic acid, and coniferyl alcohol were also different depending on the evaluated zone and the fraction used (apoplastic or symplastic). In general, each activity had a specific and unique pattern. Immunodetection of peroxidase proteins in Western blots using anti-horseradish peroxidase and anti-ascorbate peroxidase antibodies revealed different bands at the different zones of the root. Hydrogen peroxide was detected by electron microscopy and was mainly found in cell walls of epidermis (or rhizodermis), meristem, and elongating cells. The number of cell walls showing hydrogen peroxide decreased dramatically towards the root base. The results suggest that the different zones of the root show specific requirements for ascorbic acid and hydrogen peroxide. Also, each fragment of the root seems to express specific peroxidase proteins. Different processes that take place at every part of the root, as cell proliferation and elongation near the root apex and gradual lignification and differentiation towards the root base are the key to explain the results.

Ascorbic Acid↗
PubMed2002

Genotoxicity is modulated by ascorbic acid. Studies using the wing spot test in Drosophila.

The ability of ascorbic acid (Vitamin C) to modulate the genotoxic action of several mutagens was investigated in the wing spot test of Drosophila melanogaster. In this assay, 3-day-old transheterozygous larvae for the multiple wing hairs (mwh, 3-0.3) and flare (flr, 3-38.8) genes were treated with three reference mutagenic compounds, namely cobalt chloride (CoCl2), 4-nitroquinoline 1-oxide (4-NQO) and potassium dichromate (K2Cr2O7). The results obtained show that the three reference mutagens tested were clearly genotoxic in the Drosophila wing somatic mutation and recombination test (SMART). None of the three concentrations tested of ascorbic acid (25, 75 and 250mM) induced significant increases in the frequency of the mutant clones recorded. When co-treatment experiments with ascorbic acid were carried out, different results were found. Thus, ascorbic acid was effective in reducing the genotoxicity of K2Cr2O7 virtually to the control level; on the contrary, it did not show any antigenotoxic effect on the genotoxicity of 4-NQO. Finally, co-treatments with CoCl2 and ascorbic acid show a significant increase in the frequency of mutant clones over the values obtained with CoCl2 alone.

4-Nitroquinoline-1-oxide↗
PubMed2003

Sodium-dependent ascorbic acid transporter family SLC23.

l-Ascorbic acid (vitamin C) is an effective antioxidant and an essential cofactor in numerous enzymatic reactions. Two Na(+)-dependent vitamin C transporters (SVCT1 and SVCT2) are members of the SLC23 human gene family, which also contains two orphan members. SVCT1 and SVCT2 display similar properties, including high affinity for l-ascorbic acid, but are discretely distributed. SVCT1 is confined to epithelial systems including intestine, kidney, and liver, whereas SVCT2 serves a host of metabolically active and specialized cells and tissues including neurons, the eye, lung, and placenta, and a range of neuroendocrine, exocrine, and endothelial tissues. An SVCT2-knockout mouse reveals an obligatory requirement for SVCT2, but many of the specific roles of this transporter remain unclear.

Animals↗
PubMedDate not supplied

Ascorbic acid turnover in the mouse following acute ozone exposure.

Swiss Webster mice were continuously exposed to an atmosphere containing 1.5 ppm ozone (O3) for 5 days. Control mice breathed filtered air. Immediately following the exposure period each mouse was then injected with [1-14C] ascorbic acid. The rate of disappearance of [1-14C] ascorbic acid and the levels of total ascorbic acid were determined in serum, lung, liver, and the remaining carcass over a 9-day period. O3 exposure caused transient decreases in the ascorbic acid levels in liver and serum, whereas lung ascorbic acid levels increased. The apparent biological half-life of ascorbate in carcasses (minus lung and liver) from O3-exposed mice, was significantly prolonged. Significant changes were also observed in the net flux of ascorbic acid in all tissues examined. The results indicated that the change in ascorbic acid levels in a given tissue appeared to reflect changes in the rate of ascorbic acid degradation, its mobilization or tissue compartmentalization, rather than increased synthesis in response to O3 exposure.

Animals↗
PubMed1982

[Plasma ascorbic acid in hemodialysis patients: preliminary results].

Ascorbic acid plasma concentration was investigated in 10 patients undergoing chronic hemodialysis and in 10 normal subjects. Ascorbatemia was measured by a specific enzymatic method. The mean ascorbatemia of hemodialysed patients was 0.285 +/- 0.120 mg%; in normal subjects was 0.604 +/- 0.119 mg%: the difference was statistically very significative, P less than 0.01. Moreover, the vitamin C alimentary intake was investigated in all subjects: in the controls it was constantly over 100 mg/die, but in hemodialysed patients it was nearly 40 mg/die because of their vegetable and fruit dietary restriction. It was found a positive correlation between potassium and ascorbic acid alimentary intakes. The decreased alimentary intake and the loss during dialysis can explain the low ascorbatemia of hemodialysed patients.

Adult↗
PubMed1975

Acylation of ascorbic acid in water.

The acylation of ascorbic acid by acetic anhydride was studied in water at 25 degrees. The results indicate that the initial products of reactions between these two compounds were acetic acid and 3-o-acetylascorbic acid. The latter product then underwent two parallel reactions: hydrolysis to ascorbic and acetic acids and an intramolecular O leads to O acyl migration to yield-O-acetylascorbic acid. The former reaction was predominant at pH values below 4, whereas the latter reaction predominated at pH values between 4 and 7. These results are used as a basis for questioning the structural assignments previously made to some ascorbic acid esters.

Acetylation↗
PubMed1982

The effect of ascorbic acid supplementation on periodontal tissue ultrastructure in subjects with progressive periodontitis.

In an attempt to determine the optimal daily ascorbic acid requirement, the effect of different levels of ascorbic acid intake on collagen synthesis was studied in a double-blind experimental design. By use of electron microscopy, interproximal gingival tissue sections in subjects consuming between 20 to 35 mg of ascorbic acid daily were examined before and after the administration of tablets containing 70 mg of ascorbic acid. The results showed that practically all subjects were affected by progressive periodontitis with marked changes in the connective tissue of the gingival lamina propria. After six weeks of supplementation with ascorbic acid, differences in the shape and activity of fibroblasts in the regenerative tissue of lamina propria were observed. This has resulted in the increased number of collagen bundles in fibroblasts' periphery, increased tonofibril content and an enlarged number of desmosomes between adjacent cells. It is concluded that the obtained results, though suggesting that the optimal daily ascorbic acid intake should be set above the presently recommended 30-50 mg, have to be quantified by a more objective analytical method.

Adult↗