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PubMed1984

[Recent knowledge concerning the biochemistry and significance of ascorbic acid].

The ascorbic acid plays an important part by activation of hydroxylation reactions in various biosyntheses, such as in that of tropocollagen, bile acids and carnitine. It also considerably participates in the detoxication of compounds by hydroxylation and in the maintenance of the cytochrome P 450 contents in the liver. A sufficient supply is of importance for the absorption and accumulation of iron as well as for the efficiency of the immune system. After application of 14C-labelled ascorbic acid the compound is retained mainly in the brain, the salivary glands, the adrenal glands, the testes and in the eye lens. The largest contents of ascorbic acid lies in the pituitary gland, in the adrenal glands and in the eye lens. The need of ascorbic acid varies in man in dependence upon the state of development and the loads between 30 and 60 mg/die. In great smokers, after operations and traumas as well as when infections are present the intake of 100 to 200 mg a day are recommended. When more 1 g a day are taken the utilization decreases, the decomposition and the excretion, respectively, increase. A dose of more than 2 g a day inhibits the phagocytosis activity of leucocytes.

Age Factors↗
PubMed1990

Effect of ascorbic acid supplementation on haematological response and ascorbic acid status of young female adults.

Haematological response and ascorbic acid (AA) status were evaluated in 32 young adult females (age 20-34 years) 8 weeks after supplementation with two levels of AA (50 and 100 mg). Both levels of AA intake produced a similar response marked by significant elevation (p less than 0.01) in Hb concentration, Hct level, RBC count, serum and leucocyte ascorbate concentrations. Ten weeks after withdrawal of the supplements, values for all parameters evaluated decreased significantly (p less than 0.01) to presupplementation levels. Haemoglobin concentration and leucocyte ascorbate remained relatively higher (p less than 0.01) than initial values in subjects who received 100 mg AA. This study showed that AA supplementation improved erythropoietic activity and AA status of our female population. However, the higher dose of AA (100 mg) sustained Hb concentration and tissue ascorbate longer after withdrawal of supplementation.

Adult↗
PubMed2003

Changes in catecholamine metabolism by ascorbic acid deficiency in spontaneously hypertensive rats unable to synthesize ascorbic acid.

We have previously reported the establishment of a novel rat strain, SHR-od, with both spontaneous hypertension and a defect of ascorbic acid biosynthesis. Blood pressure in mature SHR-od fed an ascorbic acid-supplemented diet is over 190-200 mmHg, while it decreased to around 120 mmHg at 4-5 weeks after the cessation of ascorbic acid supplementation. With regard to possible mechanisms of blood pressure lowering, we focused on catecholamine synthesis in adrenal glands, since catecholamine is a major factor for blood pressure regulation and ascorbic acid is a co-factor of dopamine beta-hydroxylase (DBH) in catecholamine biosynthesis. Male SHR-od (25-week-old) and normotensive ODS rats with a defect in ascorbic acid biosynthesis (25-week-old) were fed a Funabashi-SP diet with or without ascorbic acid (300 mg/kg diet) for 28 days or 35 days. In SHR-od, systolic blood pressure (191 +/- 6 mmHg) began to decrease from day 21 in the ascorbic acid-deficient group, whereas no significant difference was found in ODS rats. In spite of significant lowering of blood pressure, no significant differences were found in catecholamine levels in serum, adrenal glands and brain on day 28. On day 35, however, urinary excretion of norepinephrine and epinephrine in the ascorbic acid-deficient SHR-od were higher at 490% (P < 0.05) and 460% (P < 0.05) of the respective control. Serum catecholamine concentrations and the adrenal catecholamine content tended to be higher in the ascorbic acid-deficient SHR-od than the control of SHR-od and reached to similar level in ODS rats. The administration of ascorbic acid (intraperitoneal injection, 60 mg ascorbic acid/kg body weight, once a day) to the ascorbic acid-deficient SHR-od restored blood pressure to the range 180-190 mmHg within two days. These findings indicate that ascorbic acid deficiency affects catecholamine metabolism in the adrenal glands of SHR-od in response to blood pressure lowering, suggesting catecholamines are not involved in the mechanism for the remarkable reduction in blood pressure in response to ascorbic acid deficiency.

Adrenal Glands↗
PubMed1998

Ascorbic acid levels in maternal milk: differences with respect to ascorbic acid status during the third trimester of pregnancy.

The aim of the present investigation was to study the relationship between ascorbic acid status during the third trimester of pregnancy and levels of this vitamin in transition milk (days 13-14 of lactation) and mature milk (day 40 of lactation). To this end, the pregnancies and lactation periods of fifty-seven healthy women between 18 and 35 years of age (27 (SD 3.7) years) were monitored. Vitamin intake during the third trimester was determined by recording the consumption of foods over 5 d, and by registering the quantities provided by dietary supplements. Ascorbic acid levels in maternal serum during this stage of pregnancy, and in transition and mature milk samples, were determined by spectrophotometry. Those subjects with ascorbic acid intakes below that recommended (80 mg/d) (group L) showed lower consumption of fruit and vegetables than did those with greater intakes (group H). The consumption of ascorbic acid supplements was very low, and was only seen in three group H subjects. The difference in ascorbic acid intake was reflected at serum level. Group L subjects showed significantly lower serum values than did group H subjects (30.1 (SD 36.3) mumol/l compared with 101.1 (SD 168.1) mumol/l). Vitamin intake also influenced the composition of transition milk. Group L subjects showed significantly lower levels of ascorbic acid in milk than did group H subjects (255.5 (SD 220.3) mumol/l compared with 437.8 (SD 288.4) mumol/l). The results of the present study reveal the need to increase the consumption of fruits and vegetables during pregnancy and to monitor maternal ascorbic acid intake and vitamin C status.

Adolescent↗
PubMed1975

Automated constant-current coulometric assay system for ascorbic acid and sodium ascorbate.

The performance of an automated constant-current coulometric system for the assay of ascorbic acid and sodium ascorbate is described. After loading, it is capable of analyzing 25 samples and printing out the titer values with no operator attention for 2.5 hr. Under optimum conditions, ascertained by evaluating various electrochemical parameters, the accuracy and precision (95% ts) were found to be +/- 0.3%.

Ascorbic Acid↗
PubMed2003

Pulmonary bioavailability of ascorbic acid in an ascorbate-synthesising species, the horse.

Vitamin C (ascorbic acid) is a non-enzymatic antioxidant important in protecting the lung against oxidative damage and is decreased in lung lining fluid of horses with airway inflammation. To examine possible therapeutic regimens in a species with ascorbate-synthesising capacity, we studied the effects of oral supplementation of two forms of ascorbic acid, (each equivalent to 20 mg ascorbic acid per kg body weight) on the pulmonary and systemic antioxidant status of six healthy ponies in a 3 x 3 Latin square design. Two weeks supplementation with ascorbyl palmitate significantly increased mean plasma ascorbic acid concentrations compared to control (29 +/- 5 and 18 +/- 7 micromol/l, respectively; p < 0.05). Calcium ascorbyl-2-monophosphate, a more stable form of ascorbic acid, also increased mean plasma ascorbic acid concentrations, but not significantly (23 +/- 1 micromol/l; p = 0.07). The concentration of ascorbic acid in bronchoalveolar lavage fluid increased in five out of six ponies following supplementation with either ascorbyl palmitate or calcium ascorbyl-2-monophosphate compared with control (30 +/- 10, 25 +/- 4 and 18 +/- 8 micromol/l, respectively; p < 0.01). Neither supplement altered the concentration of glutathione, uric acid or alpha-tocopherol in plasma or bronchoalveolar lavage fluid. In conclusion, the concentration of lung lining fluid ascorbic acid is increased following ascorbic acid supplementation (20 mg/kg body weight) in an ascorbate-synthesising species.

Animals↗
PubMed1998

Spontaneous conversion of L-dehydroascorbic acid to L-ascorbic acid and L-erythroascorbic acid.

Dehydroascorbic acid, an oxidation product of ascorbic acid (vitamin C), spontaneously decomposed at neutral and higher pH levels to form three products that could be quantitated by HPLC-electrochemical analysis. One of the products was ascorbic acid, suggesting that dehydroascorbic acid was reduced to ascorbic acid without adding an exogenous reductant. The major newly produced compound was almost identical to ascorbic acid by UV spectroscopy, which therefore potentially interfered in the study of ascorbic acid metabolism. The ascorbic acid-like compound was isolated by reversed-phase HPLC and identified as L-erythroascorbic acid by mass spectrometry. Fe(II) and Cu(I) increased, whereas desferrioxamine, a potent iron chelator, inhibited L-erythroascorbic acid production. Phosphate, used as buffer, and cyanide greatly enhanced dehydroascorbic acid conversion to L-erythroascorbic acid. The identification of L-erythroascorbic acid and its quantitation by an electrochemical method provides a useful tool for future study of dehydroascorbic acid metabolism.

Ascorbic Acid↗
PubMed1987

Effect of dietary ascorbic acid, cholesterol and PCB on cholesterol concentrations in serum and liver in a rat mutant unable to synthesize ascorbic acid.

The effect of ascorbic acid deficiency and excessive ascorbic acid intake on serum and liver levels of cholesterol and lipids was investigated in ODS-od/od (OD) rats fed a normal diet, a cholesterol-containing diet or a polychlorinated biphenyl (PCB)-containing diet. The OD rat is a rat mutant unable to synthesize ascorbic acid. In OD rats, the dietary requirement of ascorbic acid to maintain normal growth and normal levels of cholesterol in serum and liver is about 300 mg of ascorbic acid/kg diet. In control (ODS-+/+) rats that can synthesize ascorbic acid, dietary addition of 0.5% cholesterol and 0.25% cholic acid caused elevation of cholesterol concentrations in serum and liver, elevation of total lipids in liver and reduction of the ratio of high density lipoprotein (HDL) cholesterol to total cholesterol in serum. Dietary addition of PCB (200 mg/kg diet) caused elevation of serum concentration of cholesterol and of the ratio of HDL-cholesterol to total cholesterol in serum. In OD rats fed a normal diet, ascorbic acid deficiency slightly elevated serum concentration of cholesterol, elevated liver concentration of cholesterol and reduced the ratio of HDL-cholesterol to total cholesterol in serum; and ascorbic acid excess did not affect serum and liver concentrations of cholesterol and the ratio of HDL-cholesterol to total cholesterol in serum. In OD rats fed a cholesterol-containing diet, ascorbic acid deficiency elevated serum and liver concentrations of cholesterol, and did not affect the ratio of HDL-cholesterol to total cholesterol in serum; and ascorbic acid excess did not affect serum and liver concentrations of cholesterol and the ratio of HDL-cholesterol to total cholesterol in serum.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Ascorbic acid absorption in Crohn's disease. Studies using L-[carboxyl-14C]ascorbic acid.

Total body pool and intestinal absorption of ascorbic acid were studied in 12 patients undergoing operation for Crohn's disease (six with fistulae and six without) and in six control patients undergoing operation for reasons other than Crohn's disease. L-[carboxyl-14C]Ascorbic acid, 0.19-0.40 megabecquerels (MBq), was given orally. After a period of equilibration, the labeled ascorbic acid was flushed out of the patient's body tissues using large doses of unlabeled ascorbic acid. Intestinal absorption of ascorbic acid, assessed from the total cumulative urinary 14C recovery, was found to be similar in patients with fistulizing Crohn's disease (73.9 +/- 8.45%), those without fistulas (72.8 +/- 11.53%), and in controls (80.3 +/- 8.11%). Total body pools of ascorbic acid, calculated using the plasma 14C decay curves, were similar in patients with Crohn's disease with fistulas (17.1 +/- 5.91 mg/kg), patients without fistulas (9.6 +/- 3.58 mg/kg), and in controls (13.3 +/- 4.28 mg/kg). The results indicate that ascorbic acid absorption is normal in patients with both fistulizing and nonfistulizing Crohn's disease. The results suggest that routine supplements of vitamin C are not necessary unless oral ascorbic acid intake is low.

Adult↗