Effects of erythorbic acid on vitamin C metabolism in young women.

Erythorbic acid, an epimer of L-ascorbic acid, is used in the United States as a food additive. Studies were conducted to determine whether the ingestion of erythorbic acid in the diet had any beneficial or adverse effects on the human requirement for vitamin C. Young women were fed diets that contained controlled amounts of erythorbic acid and ascorbic acid. In pharmacokinetic evaluations, erythorbic acid and ascorbic acid were rapidly absorbed with little interaction. Erythorbic acid cleared from the body more rapidly than ascorbic acid. Some subjects received diets deficient in vitamin C for periods < or = 30 d. Increasing intakes of erythorbic acid or prolonged intakes of < or = 1 g erythorbic acid/d did not indicate any interactions with ascorbic acid. Consumption of erythorbic acid resulted in the presence of erythorbic acid in mononuclear leukocytes. Ascorbic acid concentrations in these cells were not affected by the presence of erythorbic acid. Erythorbic acid disappeared quickly from these cells with cessation of erythorbic acid supplements. Prolonged ingestion of erythrobic acid by young women neither antagonized nor spared their vitamin C status.

Refrigeration of blood samples prior to separation is essential for the accurate determination of plasma or serum zinc concentrations.

An evaluation of refrigeration (7 degrees C) to prevent falsely high plasma or serum zinc concentrations owing to elapsed time between blood collection and centrifugation was performed. At room temperature (23 degrees C), both plasma and serum zinc concentrations increased significantly, if blood samples were stored uncentrifuged. Plasma zinc concentrations increased 6.3% at 1 h and 40.7% at 24 h, whereas serum zinc concentrations increased only 0.9% at 1 h and 12.5% at 24 h at room temperature. When blood samples were stored uncentrifuged in the refrigerator for up to 24 h, there were no significant increases in zinc concentrations in either plasma or serum. These findings suggest that plasma or serum separation should be performed immediately after blood drawing to obtain accurate zinc concentrations, and if this is not feasible, the samples should be immediately refrigerated and separation performed within eight hours.

Dietary folate requirement determined for channel catfish, Ictalurus punctatus.

Juvenile channel catfish, Ictalurus punctatus, were fed semipurified basal diets containing 0, 0.2, 0.5, 1.0, 4.0 or 10.0 mg/kg of folic acid or 10 g/kg of succinylsulfathiazole in aquaria for 15 wk. Fish fed the sulfonamide showed higher mortality, lower weight gain, lower thrombocyte counts, higher hemocytoblast and neutrophil counts, and lower liver folate concentrations than did control fish (0 folic acid), indicating that significant intestinal bacterial synthesis of folate occurs in channel catfish. There were positive quadratic regressions of weight gain, hematocrit, erythrocyte and leukocyte numbers, and positive linear regressions of plasma and liver folate on dietary folic acid concentrations. Broken-line analysis showed that the dietary requirements for folic acid for optimum weight gain, hematocrit, and erythrocyte and leukocyte numbers were 1.01, 1.17, 1.12 and 1.15 mg/kg, respectively. Plasma and liver concentrations of folate associated with normal growth and hematopoiesis were 22.9 nmol/L and 20.0 nmol/g, respectively. Ratios of leukocytes and lymphocytes to erythrocytes were maximal in fish fed 4.0 mg folic acid/kg, indicating that immunocompetence may increase as the dietary dose exceeds that required for normal growth. Anemia in folate-deficient channel catfish was characterized by pale livers, spleens, gills and kidneys, and by poikilocytosis, anisocytosis, pyknosis, cytoplasmic clearing, increased numbers of hemocytoblasts, macrocytosis, and binucleated erythrocytes or "spectacle" cells.

Effect of smoking on folate levels in buccal mucosal cells.

The objective of the study was to document the existence of localized deficiency of folate in a tissue exposed to cigarette smoke, by analysis of oral and circulatory levels of this vitamin in smokers and non-smokers. Buccal mucosal cells and blood samples were collected from 25 smokers and 34 non-smokers. The Health Habits and History Questionnaire was completed by each subject. A 96-well plate L. casei assay, along with preincubation with a folate-free chick pancreas pteroyl-gamma-glutamyl hydrolase, was used to quantitate total buccal mucosal cell folates. The reproducibility (CV 5 to 7%) and recovery (95 to 106%) of the folate assay were satisfactory. Smokers had significantly lower buccal mucosal cell folate levels than did non-smokers. The mean plasma folate level of smokers although within normal limits, was also significantly lower than that of non-smokers. There were no significant differences in mean dietary folate intake or in alcohol consumption between the 2 groups. The strength of the positive association between smoking and plasma and buccal mucosal cell folate deficiency (by any definition) was moderate to strong and statistically significant. Our results indicate that cigarette smoking may result in a localized folate deficiency in buccal mucosal cells, independent of the plasma folate levels.

Maternal serum folate and zinc concentrations and their relationships to pregnancy outcome.

To evaluate the relationship between folate and zinc, and its effect on pregnancy outcome, maternal serum folate and zinc concentrations were determined at 18 and 30 wk gestation in a defined population of 285 pregnant women as part of a large-scale study to identify risk factors for fetal growth retardation (FGR). These results were correlated with birth weight and Apgar scores of newborn infants and with maternal infections during the perinatal period. A weak linear relationship was observed between maternal serum folate and zinc concentrations at 30 wk gestation. Folic acid supplementation had favorable effects on birth weight and Apgar scores of newborns, and reduced prevalence of FGR and maternal infections. No significant correlation was found between serum zinc concentration and birth weight of infants. The concept that folic acid supplementation has an adverse effect on maternal zinc nutriture and pregnancy outcome was not supported.

Long-term treatment of the MRL/lpr mouse with methotrexate and 10-deazaaminopterin.

Female MRL/lpr mice were treated with I.P. doses of methotrexate (MTX) and 10-deazaaminopterin (DAAM) in the range of 1 to 100 mg/kg body weight/week, in two equally divided doses. Treatment began at 7 weeks of age and continued to 30 weeks of age. Joint histopathology scores were tightly correlated with skin lesion-proteinuria scores at 30 weeks of age. MTX at levels of 5, 25, and 100 mg/kg body weight/week and DAAM at a level of 25 mg/kg body weight/week significantly reduced skin lesion-proteinuria scores below controls in a dose dependent manner. Animals receiving MTX at 25 mg/kg body weight/week had a significantly longer median life span and animals receiving MTX at 100 mg/kg body weight/week had a greater than 15% suppression of growth when compared with controls. Longevity and skin lesion-proteinuria scores appeared to be good indicators of drug efficacy while growth suppression appeared to be a good indicator of drug toxicity.

Influence of dietary intakes of erythorbic acid on plasma vitamin C analyses.

D-Erythorbic acid is an epimer of L-ascorbic acid, but lacks antiscorbutic activity. It is commonly used as a food additive, particularly in processed meat items. Except for high-performance liquid chromatography (HPLC) methodology, the commonly used analytical procedures to measure vitamin C do not distinguish between the two isomers. A study with seven adult women demonstrated that the concentration of erythorbic acid present in food items commonly consumed was sufficient to produce interference in plasma vitamin C analyses. With the meals used, 7-23% of the apparent vitamin C in plasma obtained 2 h after the ingestion of the meals was actually erythorbic acid when analyzed by HPLC. To avoid falsely high plasma-serum vitamin C values as a result of erythorbic acid ingestion, the analyses should be conducted on overnight fasting blood specimens or with the use of an HPLC-amperometric method.