Influence of ascorbic acid supplementation on copper status in young adult men.

The influence of ascorbic acid supplementation on the copper status of young adult men was investigated. Subjects consuming self-selected diets took 500 mg of ascorbic acid with each meal (1500 mg/day) for 64 days. Blood samples were obtained at 0, 28, 52, and 64 days in order to determine serum copper and serum ceruloplasmin. Each subject thus served as his own control. Analyses were repeated 20 days after the ascorbic acid supplement was terminated. Serum ceruloplasmin activity was significantly reduced (p less than 0.01) at every data point throughout the ascorbic acid supplementation period. A similar but nonsignificant trend was observed for serum copper. Furthermore there was a significant increase (p less than 0.01) in serum copper concentration 20 days after the supplementation period. Although observed effects occurred within physiological ranges of normal values, this study confirms that a high ascorbic acid intake is antagonistic to copper status of men as has been demonstrated in laboratory animals.

Fluoride content of foods made with mechanically separated chicken.

The goal of the present study was to determine the extent to which foods made with mechanically separated chicken can contribute to total fluoride intake. Fluoride content of each blended sample was determined with a fluoride combination electrode following perchloric-acid-facilitated diffusion of hydrogen fluoride. Infant foods had the highest fluoride content followed by chicken sticks, luncheon meats, and canned meats. A single serving of chicken sticks alone would provide about half of a child's upper limit of safety for fluoride. Fluoride content of foods made with mechanically separated chicken was significantly correlated with calcium content, which is consistent with the possibility that the mechanical separation process was the source of the extra fluoride. Foods made with mechanically separated turkey were not a major source of fluoride.

Influence of dietary lead on fluoride bioavailability in the rat.

A factorial experiment was conducted with weanling rats fed a purified diet to determine the influence of dietary lead (0 or 100 ppm) as either lead acetate or lead carbonate on fluoride bioavailability (2 or 10 ppm as sodium fluoride). During the 6-wk study, both forms of lead depressed weight gain, regardless of the fluoride level, despite the fact that food intake was similar for all treatment groups. Both forms of lead produced a small, but significant, reduction in femur and second molar fluoride. This effect, however, could only be demonstrated in rats fed diets containing 10 ppm fluoride, indicating a significant interaction between lead and fluoride for these indices of fluoride bioavailability. This interactive effect between fluoride and lead was also demonstrated for apparent fluoride absorption. Both forms of dietary lead significantly increased the lead concentration of plasma, femur, liver, and kidney, and both forms of lead significantly increased the urinary excretion of delta-aminolevulinic acid. The level of dietary fluoride failed to influence these measurements. We therefore conclude that, although small amounts of dietary lead reduce fluoride bioavailability, small amounts of dietary fluoride do not appear to significantly influence the utilization of dietary lead.

Increased plasma pyridoxal-5'-phosphate when alkaline phosphatase activity is reduced in moderately zinc-deficient rats.

It is generally believed that the zinc metalloenzyme alkaline phosphatase is required to hydrolyze phosphorylated forms of vitamin B-6 prior to their use. To test this hypothesis, rats were fed a liquid diet containing either adequate or moderately low zinc during gestation and lactation. Zinc deficiency was produced in dams evidenced by significant reductions in zinc concentration of plasma (49%), liver (25%), and femur (24%), and plasma alkaline phosphatase activity (48%). Plasma pyridoxal-5'-phosphate (PLP), which significantly increased (61%) in these same rats, was negatively correlated (r = -0.74, P < 0.02) with plasma alkaline phosphatase activity. Maternal liver PLP concentration was unaffected by zinc status. The zinc and vitamin B-6 relationship seen in dams was less observable in offspring. Stimulation of erythrocyte alanine aminotransferase activity by exogenously added PLP in vitro tended to be higher in both moderately zinc-deficient mothers and their offspring, but the difference was not significant. Our results support the hypothesis that alkaline phosphatase activity is required for the hydrolysis of plasma PLP. Our results also suggest that zinc status as alkaline phosphatase activity should be defined in an individual if plasma PLP is to be used as an indicator of vitamin B-6 status.

Effect of dietary fluoride on selenite toxicity in the rat.

Three factorial experiments were conducted to determine if high dietary fluoride (F) would inhibit selenite toxicity in rats. Initially, three levels of selenite (0.05, 3, and 5 mg/kg diet) were matched against three levels of F (2, 75, and 150 mg/kg diet). Fluoride failed to prevent the depressive effect of selenite on 8-wk food intake and body wt gain. Selenium (Se) concentration of plasma and kidney and enzymatic activity of whole blood glutathione peroxidase (GSH-Px) were also unaffected by F. Liver Se concentration, however, was slightly (12%) but significantly (p < 0.025) reduced when the highest F and Se levels were combined. Fluoride (150 mg/kg) appeared to reduce liver selenite toxicity (5 mg/kg). Therefore, further study focused on liver histology with treatments that eliminated the middle levels of selenite and F. Fluoride prevented the hepatic necrosis seen in selenite-toxic rats. Similar histological lesions were not observed for kidney or heart. Fluoride partially (26%) but significantly (p < 0.025) reduced thiobarbituric-reactive substances in selenite-toxic rats, but there was no F effect on intracellular distribution of liver Se, glutathione levels in liver and kidney, or on liver xanthine oxidase activity. Overall, the protective effect of F on selenite toxicity appears to be confined to liver pathology. The exact mechanism for this effect, however, remains unclear.

Influence of dietary magnesium on fluoride bioavailability in the rat.

A factorial experiment was conducted with weanling rats fed a purified diet to determine the influence of dietary magnesium (200, 500 or 2500 ppm) as the carbonate on fluoride bioavailability (2 or 10 ppm as sodium fluoride). After 6 wk, rats fed the lowest magnesium-containing diets had significant reductions of plasma and femur magnesium. Higher dietary fluoride prevented accumulation of calcium in the kidneys of magnesium-deficient rats. Rats fed the lowest magnesium-containing diets had significantly more fluoride in their femurs and molar teeth than other groups at both levels of fluoride, whereas rats fed diets containing 5 times normal magnesium had less fluoride in their femurs and molars. The magnitude of the magnesium effect was considerably greater in rats fed diets containing 10 ppm fluoride compared to 2 ppm, indicating a highly significant, level-dependent interaction between magnesium and fluoride. Five-day metabolic studies conducted during wk 3 and 6 showed that low dietary magnesium significantly enhanced fluoride absorption, whereas high dietary magnesium significantly reduced fluoride absorption. Fluoride retention values simply reflected absorptive changes, which indicates that the site of the interaction between magnesium and fluoride is at the intestinal level, most likely involving insoluble complex formation.

Postabsorptive effect of increased dietary zinc on toxicity and removal of tissue lead in rats.

Weanling male albino rats were fed a diet containing 12 ppm zinc and 200 ppm lead for 3 weeks. At the end of this time a representative number of samples were collected to determine tissue zinc and lead, inhibition of the lead-sensitive liver enzyme delta-aminolevulinic acid dehydratase (ALAD), and urinary delta-aminolevulinic acid (ALA). Dietary lead exposure was terminated, and the remaining rats were fed diets containing either 12 or 200 ppm zinc. Analyses were repeated at 5-day intervals over a 15-day period after lead exposure. As expected, inhibition of liver ALAD, excretion of urinary ALA and soft tissue lead content rapidly decreased after lead was removed from the diet approaching control levels by day 15. Although high dietary zinc increased the zinc content of plasma, liver and tibia, there was little or no therapeutic effect on recovery of liver ALAD, urinary ALA excretion or on the removal of lead from liver, kidney or tibia. Removal of red blood cell lead, however, was greater for rats fed the high zinc diet. Results of this study indicate that the postabsorptive interaction between zinc and lead is considerably less important than the previously reported intestinal interaction.

Influence of dietary zinc on lead toxicity during gestation and lactation in the female rat.

Confirmed pregnant female albino rats received a purified diet containing either 12 or 120 ppm zinc with or without lead (0 to 500 ppm) from day 0 gestation through day 16 of lactation. An 11% reduction in dam weight gain during gestation and a 12% reduction in average pup weight in rats fed the low zinc plus lead diet was markedly different compared to controls not receiving lead and lead supplemented rats receiving supplemental zinc. Milk lead concentration was reduced in rats receiving additional dietary zinc and lead which was reflected in a 15% reduction in pup tibia lead concentration, a 20% reduction in inhibition of pup liver delta-aminolevulinic acid dehydratase activity and a 31% reduction in pup blood porphyrin concentration. Some of the beneficial effects of supplemental zinc on lead toxicity of pups may be explained by a reduction of both liver lead (40%) and blood lead (32%) concentration of dams. However an interaction between lead and zinc at the placental and mammary barriers must also be considered. The results of this study suggest that nutritional status of zinc may be an important factor in modifying lead burden of infants borne by women occupationally and environmentally exposed to lead.

Determination of a copper requirement to support gestation and lactation for the female albino rat.

Confirmed pregnant female albino rats were fed a purified diet containing 3, 6, 9 or 12 ppm copper throughout gestation and lactation in order to determine a copper requirement for one generation. A diet containing 6 ppm copper was found to meet the biochemical needs for rats during gestation, but the combined stress of gestation plus lactation raised the dietary requirement to 9 ppm copper. Evidence to support these conclusions included measurements of serum copper concentration, serum ceruloplasmin activity, liver iron concentration, milk copper concentration and pup liver copper concentration. The results of these studies suggests that the current National Research Council recommendation of 5 ppm does not maximize the copper status of first generation off-spring in rats.

Reduction in neonatal lead exposure by supplemental dietary iron during gestation and lactation in the rat.

Confirmed pregnant female albino rats were fed a purified diet containing either 30 or 150 ppm iron with or without lead (0 or 250 ppm) from day 0 of gestation through day 15 of lactation. A 19% reduction in dam weight gain during gestation and a 13% reduction in average pup weight in rats fed the low iron plus lead diet were markedly different compared to controls not exposed to lead and rats fed the lead-containing diet plus additional dietary iron. Milk lead concentration was reduced 34% in rats receiving additional dietary iron and lead compared to the low iron plus lead group which was reflected in almost identical reductions in pup erythrocyte and tibia lead concentrations, and a smaller reduction in pup liver lead concentration at day 15 of lactation. Determination of lead in pup liver obtained shortly after birth also suggests a possible effect of dietary iron on placental transfer of lead. Supplemental dietary iron reduced both maternal liver and blood lead concentration by 44 and 54%, respectively. Overall the results of this study show that neonatal lead exposure can be significantly reduced by providing supplemental dietary iron during gestation and lactation.

Effect of suboptimal zinc nutrition during gestation and lactation on rat molar tooth composition and dental caries.

The main objective of this study was to determine the relationship between zinc content of teeth and susceptibility to dental caries. Pregnant albino rats were fed a purified diet containing 8, 15 or 30 ppm zinc throughout gestation and lactation. Food intake of all rats was restricted to that consumed by the lowest zinc group. At day 20 of lactation, pups were weaned to a high sucrose, caries-promoting diet and orally innoculated with streptococcus mutans. Dams consuming the lowest zinc-containing diet exhibited a mild zinc deficiency as evidenced by reductions in gestational weight gain and zinc content of milk, serum and tibia when compared to other groups. All offspring survived. Pups originating from the lowest zinc group had significantly less zinc in molar enamel and dentin fractions compared to other groups at the end of a 30-day caries test period, but tibia zinc was essentially equal. This apparent pre-eruptive reduction in zinc content of enamel and dentin of offspring was associated with significantly greater dental caries score on the buccal surface. This suggests that moderate dietary zinc deficiency is sufficient to reduce the pre-eruptive zinc content of both enamel and dentin and to increase dental caries.

Influence of maternal magnesium deficiency on tissue lead content of rats.

Diets containing 150 or 600 ppm magnesium with or without 200 ppm lead were fed to rats throughout gestation and lactation to determine the influence of moderate magnesium deficiency on tissue lead content of maternal and offspring tissue. During lactation it was necessary to increase the lowest dietary magnesium level to 225 ppm. Lead caused a significant depression in both gestational weight gain and average pup weight regardless of the level of dietary magnesium. Maternal magnesium deficiency was evidenced by significant reductions in serum and tibia magnesium, a 17-fold increase in kidney calcium, and hyperemia of the ears. In offspring, however, only growth and tibia magnesium were significantly affected by the magnesium deficiency, and the maternal-fetal difference in serum and tibia magnesium concentration was maintained. Maternal magnesium deficiency resulted in significantly higher lead concentrations in dam liver, and offspring erythrocytes, liver and tibia. A mechanism for the enhanced accumulation of lead in maternal and offspring tissue as a result of maternal magnesium deficiency is not defined, but it is likely to involve enhanced intestinal lead absorption.

Enhancement of fluoride retention by low dietary chloride without manifestation of chloride deficiency in the rat.

Weanling male albino rats were fed a purified diet containing 10 ppm fluoride as sodium fluoride and 0.02, 0.04, 0.06, 0.08, or 0.10% chloride as sodium chloride for 6 wk. Food intake was unaffected by the level of dietary chloride. Rats fed diets containing either 0.02 or 0.04% chloride had significantly higher fluoride retention and skeletal uptake of fluoride than did rats fed higher chloride levels. Diets, however, had to contain 0.04% chloride or more to support normal weight gain, femur ash weight and plasma chloride concentration. The ability to enhance fluoride content of bone on a low chloride diet without undesirable effects of chloride deficiency may have important implications, since fluoride is thought to play a role in strengthening the mineral apatite structure of bone.

Potential role of ammoniagenesis in the hypocalciuric effect of phosphorus in rats.

OBJECTIVE: Hypocalciuria associated with a high phosphorus intake is known to be both a parathyroid hormone and non-parathyroid hormone dependent event. The present study was designed to define the role that ammoniagenesis may play in the non-parathyroid hormone dependent pathway. DESIGN: Male rats, initially weighing 160 g, were fed a purified diet containing, in g/kg diet, a single level of protein (200) and variable inorganic phosphorus (1.8, 4.5, 9.0) for 20 days. RESULTS: Food intake and body weight were similar for the three groups. Significant inverse correlations were found for both urinary calcium and phosphorus and for urinary ammonia nitrogen and calcium excretion (r = -0.62, p < 0.01). Urinary ammonia nitrogen excretion was highly correlated with both phosphorus intake (r = 0.89, p < 0.001) and urinary phosphorus (r = 0.88, p < 0.001). Urinary urea nitrogen tended to vary inversely with phosphorus intake. High dietary phosphorus decreased the activity of glutamine synthetase and increased the activity of glutaminase I in kidney. CONCLUSION: Tying-up some of the hydrogen ions destined for excretion by phosphorus-stimulated ammoniagenesis could reduce the interfering effect of hydrogen ion on kidney calcium reabsorption and provide a mechanism to explain why phosphorus can have a direct positive impact upon tubular calcium reabsorption.

Chloride determination in foods with ion-selective electrode after isolation as hydrogen chloride.

This report describes a sample preparation method in which chloride is isolated as hydrogen chloride from food samples prior to analysis with the chloride ion-selective electrode. Chloride analyses of selected foods with this method agreed with chloride values reported in food composition tables. Chloride analysis with the present procedure also agreed with the certified value for the chloride content of the National Bureau of Standards (NBS) Standard Reference Material, Nonfat Milk Powder. Reliability of the chloride isolation procedure was evident by the complete recovery of chloride added to food samples and a narrow range of 95% confidence limits calculated for each set of analyses. The usefulness of the chloride ion-selective electrode to determine chloride in foods is greatly enhanced by this procedure because matrix interference by other sample components is removed prior to analysis.

Interaction between ethanol and low dietary zinc during gestation and lactation in the rat.

Pregnant rats were fed individual liquid diets throughout gestation and lactation. The diets contained either 2 or 10 micrograms zinc/ml diet with or without 30% of the kilocalories supplied from ethanol. The low zinc diet produced a moderate zinc deficiency in dams evidenced by decreases in tissue zinc content, serum alkaline phosphatase activity and urinary zinc concentration. Despite the presence of high zinc content in the diet, ethanol antagonized the maternal zinc status to a level typical of that produced by the low zinc diet. The lowest zinc status, however, was found when low dietary zinc and ethanol were combined. The maternal interaction between ethanol and zinc also depressed offspring serum zinc and alkaline phosphatase activity in a similar manner. Ethanol, however, did not affect tissue content of calcium, magnesium or phosphorus, which indicates that ethanol is a specific antagonist of zinc utilization during gestation and lactation.

Formulation of a liquid diet for ethanol studies involving gestation and lactation in the rat.

This report describes the preparation of a liquid diet for rat studies involving ethanol ingestion during gestation and lactation. The control diet was formulated to contain 30% of energy from casein including methionine at 0.5 mg/kcal, 11.5% of energy from corn oil, 58.5% of energy from dextrose, cellulose, and adequate vitamins and minerals. Calculations for the isocaloric substitution of dextrose with ethanol are described as well as the use of xanthan gum to disperse and emulsify ordinary solid diet components. The use of this liquid diet as the sole source of nutrition for the rat during gestation and lactation produced energy intakes, gestational weight gains, litter sizes, percent survival to weaning and weaning weights similar to those expected of a conventional diet even when ethanol was substituted for dextrose to provide 30% of total energy.

Determination of chloride procedure based upon diffusion of hydrogen chloride.

We describe a simple, inexpensive sample preparation method that involves the isolation of chloride as hydrogen chloride from serum and urine prior to chloride analysis with the chloride ion-selective electrode. Chloride analyses of clinical chemistry standards with the present method were found to be in good agreement with analyses reported by the manufacturer. Reliability of the method is also evident by complete recovery of chloride added to serum and urine, minimal day-to-day variation of analyses, and a coefficient of variation that generally is less than 2%. An evaluation of factors influencing the procedure is also reported. The usefulness of the chloride ion-selective electrode to determine chloride in serum or urine is greatly enhanced by the sample preparation method described since matrix interference by other sample components is removed prior to analysis.

Influence of zinc and iron on dietary fluoride utilization in the rat.

Two experiments were conducted with the weanling rat fed a purified diet to determine the influence of dietary zinc (6, 30, 150 ppm) and iron (7, 35, 175 ppm) on fluoride bioavailability. Dietary fluoride in each case was 2 or 10 ppm as sodium fluoride. During a 6-wk trial, neither divalent zinc nor divalent iron affected fluoride bioavailability based on skeletal uptake of fluoride. Our studies were specifically designed to provide concepts about the effects of dietary trace element supplementation practices on dietary fluoride bioavailability especially in terms of fluoride originating from foods prepared in fluoridated water. Our results suggest that either iron or zinc can be added to foods to improve nutritional value without compromising the availability of food fluoride.