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PubMed2005

Changes in ascorbic acid and malondialdehyde in rats after exposure to mercury.

BACKGROUND: Mercury is one of the ubiquitous pollutants participating in generation of reactive oxygen species leading to the formation of oxidative stress. METHODS: Changes in plasma concentrations of ascorbic acid and malondialdehyde were measured in rats after per os exposure to different doses of mercury (as mercuric chloride) for 30 d. RESULTS: The production of ascorbic acid and malondialdehyde was related to the dosage of mercuric chloride. Within the group of rats receiving mercuric chloride in the concentration of 10 micromol/L (corresponding to the LD50 of HgCl2), the concentrations of ascorbic acid and malondialdehyde were increased by 22.19 % and by 6.88 % respectively when compared with the control group. The doses of mercuric chloride lower than LD50 reduced the production of ascorbic acid and malondialdehyde statistically. CONCLUSIONS: Mercury is one of the inducers of oxidative stress in plasma of rats. The oxidation damage caused by mercuric chloride is proven by increased malondialdehyde formation and subsequently compensated by an overproduction of ascorbic acid (Tab. 3, Ref. 22).

Animals↗
PubMed2005

Effect of ascorbic acid on microcirculation in patients with Type II diabetes: a randomized placebo-controlled cross-over study.

Manifestations of vascular disease, including microvascular changes, constitute the major part of the morbidity and mortality in diabetic patients. Oxidative stress has been suggested to play an important role in the vascular dysfunction of diabetic patients. Furthermore, epidemiological observations indicate a beneficial effect of an increased dietary intake of antioxidants. The present study tested the hypothesis that the antioxidant ascorbic acid influences microcirculatory function in patients with Type II diabetes. Patients with Type II diabetes were treated with 1 g of ascorbic acid three times a day for 2 weeks in a randomized placebo-controlled double-blind cross-over design. Microvascular reactivity was assessed by vital capillaroscopy and PRH (post-occlusive reactive hyperaemia). hs-CRP (high-sensitivity C-reactive protein), IL-6 (interleukin-6), IL-1ra (interleukin-1 receptor antagonist) and ox-LDL (oxidized low-density lipoprotein) were analysed. The results showed no significant change in microvascular reactivity assessed after 2 weeks of ascorbic acid treatment. TtP (time to peak) was 12.0+/-3.3 s before and 11.2+/-3.5 s after ascorbic acid (n=17). In comparison, TtP was 11.5+/-2.9 s before and 10.6+/-2.8 s after placebo (not significant). IL-1ra, IL-6, hs-CRP and ox-LDL did not change significantly after ascorbic acid, neither as absolute or relative values. In conclusion, in contrast with some studies reported previously, we could not demonstrate an effect of continuous oral treatment with ascorbic acid on microvascular reactivity assessed at the level of individual capillaries. Furthermore, we found no indication of an effect on inflammatory cytokines or ox-LDL.

Antioxidants↗
PubMed2003

Relations of serum ascorbic acid and alpha-tocopherol to diabetic retinopathy in the Third National Health and Nutrition Examination Survey.

The protective relation of ascorbic acid and alpha-tocopherol to the development of diabetic retinopathy has not been thoroughly evaluated in epidemiologic studies. The association of prevalent diabetic retinopathy with serum ascorbic acid and alpha-tocopherol was studied among participants with type 2 diabetes (>or=40 years) (n = 998) in the Third National Health and Nutrition Examination Survey (1988-1994); 20% of the sample (n = 199) had prevalent retinopathy. The overall odds ratio for retinopathy among participants in quartile 4 compared with quartile 1 for serum ascorbic acid was 1.3 (95% confidence interval: 0.8, 2.3), with a p for trend = 0.60 after adjustment for the confounders of smoking, race, waist/hip ratio, hypertension, and duration of diabetes. The overall odds ratio for retinopathy among participants in quartile 4 compared with quartile 1 for serum alpha-tocopherol was 2.7 (95% confidence interval: 1.6, 4.6), with a p for trend = 0.14 after adjustment for confounders. After removal of supplement users of vitamin C (n = 307) or vitamin E (n = 298), the odds ratio changed direction or was attenuated: adjusted odds ratios for retinopathy among participants in quartile 4 compared with quartile 1 for serum ascorbic acid and alpha-tocopherol = 0.7 (95% confidence interval: 0.3, 1.4) and 1.6 (95% confidence interval: 0.9, 2.9), respectively. In summary, no significant associations were observed between serum levels of major dietary antioxidants and retinopathy. Recent use of supplements for treatment of complications of diabetes may explain the direct associations.

Adult↗
PubMed1991

Biosynthesis of ascorbic acid and riboflavin in radiated germinating chickpea.

Biosynthesis of ascorbic acid and riboflavin in radiated germinating chickpea seeds was studied at ambient room temperature (20-35 degrees C). Synthesis of these vitamins increased significantly with increasing germination time up to 120 hrs depending upon the treatment (P less than 0.05). Maximum amounts of ascorbic acid, 22.32 and 16.84 mg/100 g (wet weight) were found in the 0.10 kGy samples after 120 hrs of germination in tap and distilled waters respectively. Radiation dose of 0.20 kGy resulted in the development of maximum riboflavin, 11.4 and 11.0 micrograms/g (dry weight) on germination in tap and distilled waters respectively. An overall significant linear relation (r = 0.954 to 0.957) was found between vitamin biosynthesis and germination time up to 120 hrs in both the radiated and unradiated chickpea.

Ascorbic Acid↗
PubMed1999

Serum ascorbic acid and other correlates of self-reported cataract among older Americans.

The purpose of this study was to examine the correlates of self-reported cataract among older Americans, and specifically, to determine whether serum ascorbic acid levels are associated with a decreased prevalence of cataract. A national probability survey of Americans, the Second National Health and Nutrition Examination Survey (NHANES II), was conducted between 1976 and 1980. A total of 4001 participants were included between the ages of 60 and 74 years with data on serum ascorbic acid level and other variables of interest. A total of 252 women (12%) and 164 men (9%) reported a history of cataract. Serum ascorbic acid level was inversely associated with prevalence of cataract in multiple logistic regression analyses; each 1 mg/dl increase was independently associated with a 26% decrease in cataract (P = 0.03). Other independent correlates of cataract included increasing age, female sex, smoking, and diabetes mellitus (all P<0.01). We identified four correlates of cataract among older Americans: serum ascorbic acid level, increasing age, smoking, and diabetes mellitus. Ascorbic acid, a water-soluble antioxidant found in high concentrations in the lens, may be of importance for the prevention of cataract among older Americans.

Aged↗
PubMed1975

[Blood coagulation in man during a 3-week daily rg L(+)-ASCORBIC ACID ADMINISTRATION].

A daily dose of 4 g L (+) ascorbic acid administered for 3 weeks showed no significant influence on coagulation of venous blood, as determined by thromboelastography. The investigation was carried out on 11 healthy men aged from 25 to 45 with no history of abnormal blood clotting. The mean values of 7 different coagulation parameters are given, the differences in these parameters in individual subjects (before and after administration of ascorbic acid) being checked for significance by means of the Wilcoxon test for pair differences. The values found are comparable with those in the literature.

Adult↗
PubMed1987

Disulfide inhibition of copper-catalyzed oxidation of ascorbic acid: spectrophotometric evidence for accumulation of a stable complex.

Copper-catalyzed oxidation of ascorbic acid was retarded in the presence of the biological disulfide compounds cystine and oxidized glutathione. The evidence suggested that this effect was due to the formation of a stable complex involving the copper ion, the disulfide compound, and ascorbic acid or a derivative formed during the oxidative process. This indicated that less copper was available for the formation of oxygen complexes which are not as stable as the disulfide complexes. Ellman's reagent (Nbs2) was reduced when it was substituted for the biological disulfides or when added, with EDTA, to solutions in which ascorbic acid, copper ion, and the biological disulfides had been allowed to interact. The complex formed with cystine was detected at 360 nm but the glutathione complex was not detected at this wavelength. It is proposed that disruption of cystine or glutathione complexes by EDTA results in formation of 2,3-diketogulonic acid which acts as a reductant of Ellman's reagent.

Ascorbic Acid↗
PubMed1992

Determination of ascorbic acid in pharmaceuticals and urine by reverse flow injection.

Two reverse flow injection (FI) methods, using spectrophotometric detection, are proposed for the determination of ascorbic acid. Both methods are based on its reaction with the ethylenediaminetetraacetic acid-CoIII complex in a medium of 5% diethylamine. In the first method, using the peak-height FI technique, ascorbic acid is determined over the range from 2 x 10(-4) to 5 x 10(-3) mol dm-3 and in the second, using the peak-width FI method, the working range is extended (2 x 10(-3)-5 x 10(-2) mol dm-3). Both FI methods were applied to the determination of ascorbic acid in pharmaceuticals while the peak-height FI technique was also used to determine ascorbic acid in urine.

Ascorbic Acid↗
PubMed2003

Effect of ascorbic acid on endothelium-dependent vasodilatation of human arterial conduits for coronary artery bypass grafting.

OBJECTIVE: Techniques aimed at improving the performance of arterial conduits will maximize the clinical benefit achievable with coronary artery bypass surgery. Controlling oxidant stress could be a strategy for preventing early graft deterioration. We tested the effect of a free radical scavenger, ascorbic acid (vitamin C), on preserving the endothelium-dependent vasodilatation function in vitro of radial artery and internal thoracic artery. We also tested its effect on the amount of reactive oxygen species (ROS) generated by each graft. METHODS: Radial artery (RA, n=25) and internal thoracic (ITA, n=19) segments were obtained from coronary artery bypass grafting patients. Each segment was divided into 3-4 mm vascular rings and incubated with or without ascorbic acid (10(-3) mol/l) for 1 h or 72 h. Using the organ bath technique, the endothelium-dependent vasodilatation function was tested in vitro by the addition of cumulative concentrations of acetylcholine (10(-9)-10(-5) mol/l) following vasocontraction by endothelin-1 (3 x 10(-8) mol/l). ROS were measured by using chemiluminescence technique at 1-h and after 72 h incubation with or without ascorbic acid. RESULTS: There were no differences in the vasodilatation function between control and ascorbic acid group of both arteries in the 1-hour incubation experiment. However, in the 72 h incubation experiment, ascorbic acid preserved the endothelium-dependent vasodilatation function of RA compared with control group (35.8+/-2.2% vs. 25.9+/-2.1%; P=0.005), but not ITA (39+/-3.5% vs. 40.5+/-9.3%; P=0.438). After 72 h incubation, RA generated significantly more free radicals compared with 1 h (133.7+/-151.5 vs. 16.8+/-16.8 cps/mg x 100; P=0.01); however, AA has no statistically significant effect on decreasing the amount of free radicals generated by both arteries. CONCLUSIONS: In RA, ascorbic acid is able to preserve the endothelium-dependent vasodilatation function after 72 h incubation, but not after 1 h. However, the mechanism of action of AA is not completely understood. This finding could open the door for understanding the role of oxidant stress and antioxidants in preserving the endothelial function of coronary artery bypass grafts.

Aged↗
PubMed1975

Ascorbic acid changes in cultured rabbit lenses after microwave irradiation.

Whole body exposure of rabbits to microwave radiation causes a decrease in ascorbic acid in the lens. In our study, rabbit lenses maintained in culture medium (37 degrees C) were exposed to either pulsed or continuous wave S-band radiation for 10-15 min at power densities between 0 and 200 mW/cm-2. Total ascorbic acid was measured in selected lenses 1-3 days after irradiation. The temperature of the culture medium was measured during irradiation. Matched control lenses were exposed to similar time-temperature environments, but without microwave irradiation. Ascorbic acid decreased significantly in lenses exposed to microwave radiation. No differences were found, however, between irradiated and control lenses subjected to identical time-temperature conditions. At a given average power density, the time-temperature variation was independent of modulation. A decrease in ascorbic acid is apparently a direct thermal effect of microwave radiation in rabbit lens culture.

Animals↗
PubMed1995

Ascorbic acid and gastrointestinal cancer.

A literature review was made to critically evaluate the ability of ascorbic acid to modulate the incidence of gastrointestinal cancer. A comparison of preclinical, clinical, and epidemiological studies indicated that evidence for ascorbic acid as an inhibitor of carcinogenesis is stronger with regard to gastric cancer and weaker with regard to esophageal and colon/rectal cancer. Insufficient evidence currently exists regarding the oral cavity and the use of ascorbic acid in precancerous conditions such as polyposis and leukoplakia.

Animals↗
PubMed1989

Ascorbic acid concentration of human fetal tissues in relation to fetal size and gestational age.

1. Studies were carried out on the distribution of ascorbic acid in human fetal tissues with the progress of gestation. 2. Fetuses and stillborn babies varying in gestational age from 12 to 38 weeks were obtained from various Baroda hospitals. Ascorbic acid levels were determined in selected tissues: brain, adrenal, liver, kidney, lung, heart and placenta. 3. Ascorbic acid concentration in the brain was higher than that in the adrenal at all gestational ages, suggesting the importance of this vitamin in brain development. The concentrations of this vitamin in liver, kidney, lung and placenta were comparable, but that in the heart tended to be lower. In all the tissues, there was a fall in ascorbic acid during late gestation. However, the levels in tissues of stillborn babies were higher than those reported for adults.

Ascorbic Acid↗
PubMed1976

Ascorbic acid levels in stored blood and in patients undergoing surgery after blood transfusion.

Blood was obtained from 11 healthy voluteers, mixed with two standard types of anticoagulant used in blood transfusion centres and stored for 21-28 days at 4 degrees C. Leucocyte ascorbic acid (LAA) fell to deficient levels after 7 days in all cases. There were no corresponding changes in plasma ascorbic acid (PAA) levels. LAA and PAA were measured before, during and after surgery in 5 control patients who underwent definitive operations for benign peptic ulceration and in 4 patients under-going surgery for bleeding peptic ulceration. The average amount of blood administered to the latter group was 10 units. There was a fall in LAA and PAA in both groups of patients after operation. This fall had returned to normal by 7 days in the controls, but the LAA remained at a deficient level at 7 days in the patients who had bled. Deficient ascorbic acid in stored blood may contribute to low leucocyte ascorbic acid levels in patients after blood transfusion and may contribute to the increased complication rate when surgery is undertaken in these patients.

Adult↗
PubMed1975

Effect of ascorbic acid on the human electroencephalogram.

Controversy exists over whether ascorbic acid (vitamin C) in doses in excess of known physiological requirements has demonstrable biological effects. The present study reports that such megadoses of vitamin C do significantly effect an objective electrophysiological measure, i.e., electroencephalogram (EEG) driving responses to photic stimulation. Four thousand milligrams of vitamin C administered 27 and 3 hours prior to assessment produced an effect on the EEGs of 18 healthy adolescent human males that was significantly different from a placebo. Fifty milligrams of ascorbic acid administered in this manner did not produce an effect on the EEG significantly different from placebo administration.

Adolescent↗
PubMed1978

Long-term effectiveness of dietary iron and ascorbic acid in the prevention and cure of cadmium toxicity in rats.

The protective and curative effects of dietary iron and ascorbic acid on chronic (180 days) cadmium toxicity in rats were examined. Growth retardation and anemia were observed in rats fed a diet containing 50 ppm of cadmium for 180 days; during this period the contents of iron in the liver, kidney, spleen, testis, intestine, and tibia decreased and the zinc contents of the liver and kidney increased, but the calcium content of bone did not change. Addition of 400 ppm of iron and 1% of ascorbic acid to the cadmium-containing diet overcame the growth retardation and anemia due to cadmium toxicity and reduced the tissue levels of cadmium; however, it did not restore the zinc contents in the liver, kidney, and bone to normal. Similar effects were observed when these compounds were added to cadmium containing diet for 90 days after feeding the cadmium diet alone for 90 days. The glutamic-pyruvic transminase and glutamic-oxaloacetic transminase activities in the plasma of rats fed the cadmium diet increased significantly and these increases were prevented by supplementing the diet with iron and ascorbic acid. Glucose, urea, and alkaline phosphatase in the plasma and glycogen in the liver were not changed by feeding the cadmium diet for 180 days. These results indicate the long-term effectiveness of supplementing the diet with iron and ascorbic-acid for preventing and curing dietary cadmium toxicity in rats.

Animals↗
PubMed1992

Ascorbic acid and transforming growth factor-beta 1 increase collagen biosynthesis via different mechanisms: coordinate regulation of pro alpha 1(I) and Pro alpha 1(III) collagens.

The specific mechanisms of collagen induction in human dermal fibroblasts by ascorbic acid and transforming growth factor-beta 1 (TGF-beta 1) and their effect in combination are uncertain. Collagen synthesis and steady-state levels of pro alpha 1(I) and pro alpha 1(III) collagen RNA were examined in human dermal fibroblasts treated with 100 microM ascorbic acid, 2.5 ng/ml TGF-beta 1, or both. Within 72 h ascorbic acid and TGF-beta 1 had increased collagen synthesis by 2.55 +/- 0.32- and 1.98 +/- 0.13-fold, respectively; in the presence of both, collagen synthesis increased 4.51 +/- 0.74-fold, appearing additive. Ascorbic acid acts specifically by increasing relative collagen synthesis whereas TGF-beta 1 increases overall protein synthesis. Steady-state levels of the pro alpha 1(I) collagen (5.8 and 4.8 kb) and pro alpha 1(III) collagen (5.4 and 4.8 kb) mRNAs were examined independently. Under each condition the steady-state levels of the longer transcripts for pro alpha 1(I) and pro alpha 1(III) collagens appeared coordinately and preferentially elevated. In the presence of both ascorbic acid and TGF-beta 1 the steady-state RNA levels did not increase in an additive manner, suggesting that the additive increase in collagen synthesis results from additional post-transcriptional mechanisms.

Ascorbic Acid↗
PubMed1998

[Determination of ascorbic acid and its stability of Fructus Hippophae fruit by the method of high-valence iron reduction].

The high-valence iron reduction method was used to determine the ascorbic acid of fructus hippophae fruit. The reduction method had simple, high sensitivity and accuracy in comparison with fluorospectrophotometry or indophenol titration method. Its limit of detection was 0.01 microg/mL, the relative standard deviation and the average recovery was 0.83% (n = 8) and 95.6% (n = 6) respectively. We also researched the influence of the environment factors (temperature, storage period and condition, pH value) on the stability of ascorbic acid in fructus hippophae fruit. The ascorbic acid in fructus hippophae fruit was more stable than thepure ascorbic acid on the same condition of heating (80 C,1 hour), in pH neutral or storing in the refrigerator.

Ascorbic Acid↗

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