Harold G. Petering

Trace Metal Content of Hair

Cadmium and lead content of hair of males and females was found to he age-dependent. Regression analysis showed two male groups with respect to cadmium, namely those under and those over 12 years of age, while the data revealed only one male group with respect to lead. Analysis of the data also indicated that hair cadmium distribution for females delineated one group below, and one above, 50 years. Females showed hair lead which fell into two groups, one below and the other above 30 years of age. Cadmium and lead in the hair of both sexes showed a high degree of association of the metals (r= 0.4052 (P = .001) for males and r = 0.2563 (P = .02) for females). The data indicate that comparisons of metallic content of hair in humans must be limited to a narrow age range and to one sex.

Interaction of zinc and lead on δ-aminolevulinate dehydratase

Rat erythrocyte δ-aminolevulinate dehydratase (ALA-D) has been confirmed to be an enzyme dependent on dietary zinc. Levels of blood ALA-D decreased substantially during the first five weeks after weaning and remained constant thereafter. Dietary lead (200 ppm) caused a dramatic fall in erythrocyte ALA-D activity and, following the removal of lead exposure, the return of the enzymatic activity toward normal values was quicker in the animals receiving higher zinc than in those on lower zinc diet. Furthermore, in vitro addition of zinc to erythrocyte preparation obtained from rats exposed to dietary lead reactivated ALA-D to control values. Maximal enzymatic activity in both lead-fed and control animals occurred at 10 −4 M ZnCl 2 . There seems to be a competition between Pb ++ and Zn ++ in binding to the enzyme, with Pb ++ as inhibitor and Zn ++ as activator.

Studies of Zinc Metabolism in the Rat

Nutritional zinc can be studied in the male rat as a pharmacologic agent. Responses to zinc in respect to body growth, hematologic effects, blood and tissue levels, and body temperature control are all log-dose related. Copper levels in liver and kidney are influenced by zinc intake. Cadmium alters these responses inversely in relation to the zinc intake, and thus can be considered as an antimetabolite of zinc. Cadmium was localized in liver and kidney but not in testes of our animals. Our data indicate that there is very minimal storage of readily available zinc in the male rat.

Atomic absorption determination of zinc, copper, cadmium, and lead in tissues solubilized by aqueous tetramethylammonium hydroxide

Abstract Rat liver and kidney homogenates and homogeneous rat hair samples were prepared for atomic absorption spectrophotometric analysis by digestion with an appropriate concentration of aqueous tetramethylammonium hydroxide (TMAH). The endogenous tissue levels of Zn, Cu, Cd and Pb, the reproducibility of the analyses, and the recovery of added metal standards compare favorably with the results obtained by standard wet ashing procedures using concentrated nitric acid or nitric-perchloric acids. The use of 5% HNO 3 standard curve in calculations for the TMAH-treated samples leads to slightly lower results compared to the method of additions due to viscosity and surface tension effects on the aspiration rate of these samples. Moreover, the TMAH digestion method allows faster and safer processing and handling of samples in comparison to acid digestion procedures.

δ-Aminolevulinate dehydratase, a zinc dependent enzyme

Abstract Erythrocyte and liver tissue δ-aminolevulinate dehydratase activity was determined in rats fed a semipurified diet under controlled nutritional intake of zinc and copper. A significant decrease in enzymatic activity was observed in animals fed low zinc diet, while dietary copper had no effect. In vitro addition of zinc to the erythrocyte preparations obtained from rats on low zinc diet produced a slight increase in enzymatic activity. It appears that, even though zinc may be the metal ion activator of δ-aminolevulinate dehydratase, the requirement of this metal is at the site of synthesis of this enzyme.

Influence of dietary zinc on lead toxicity in rats

Abstract The influence of dietary zinc (5 and 50 μg/ml of drinking water) on the toxicity of lead (100 μg/ml) was studied in rats fed a semipurified diet for 140 days. Results indicated that high dietary zinc reduced the lead levels in various tissues. The antagonism between lead and zinc was also manifested by reduction of zinc levels in plasma, liver and tibia of the lead-exposed animals. Lead exposure, as expected, produced an elevation of urinary δ-aminolevulinic acid (U-ALA) throughout the experiment. This increase, however, was greater in the animals receiving low zinc. Erythrocyte zinc protoporphyrin (ZPP) was not only affected by lead, but also by dietary zinc and by the age of the rats. As expected, linear regression analysis of the data showed that RBC-Pb correlated highly with δ -aminolevulinic acid dehydratase (ALA-D), ZPP and U-ALA; moreover, plasma zinc also correlated with RBC-Pb and ZPP.

Trace Metal Content of Maternal and Neonate Hair

Hair samples were taken from mothers and newborns. The mean lead value of infants’ head hair was found to be higher than that found in many older children and was suggestive of placental lead transfer. There was a significant correlation between maternal copper in hair and infants’ lead in hair. As the age of the mother increased the copper levels in the infants’ hair decreased. The mean values of zinc decreased in mothers as parity increased. Mean hair lead values were significantly higher in blacks than in whites. The infants’ hair copper values increased as the parity of the mothers’ increased only in blacks. Zinc and iron content of infants’ hair was higher than mothers’ hair. There may be a need to screen certain populations during pregnancy so that corrective measures can be taken.

Interferences in the Determination of Metallic Elements in Human Hair: An Evaluation of Zinc, Copper, Lead, and Cadmium, Using Atomic Absorption Spectrophotometry

Hair, a metabolic end product, has been used to indicate health status. Our purposes in this study were: (1) to evaluate the hair digest matrix as a source of interferences in the determination of metals using atomic absorption spectrophotometry, and (2) to develop a technique whereby meaningful interlaboratory comparison of analytical data can be made. We have demonstrated that for hair analysis, Interferences due to broad-band nonspecific molecular absorption, chemical ionization, flame emmission, flame scatter, light scatter, and matrix matching can be avoided using ordinary methods and commercially available equipment. We have also presented a technique for the preparation of a standard reference hair sample. This standard reference hair was then used to demonstrate that concentrations of copper, zinc, lead, and cadmium in a nitric acid hair digest matrix can be measured with precision and accuracy.

Effect of sex on oral cadmium dose responses in rats: blood pressure and pharmacodynamics.

Abstract Male and female weanling Sprague-Dawley rats were fed a commercial diet and given 0.0, 4.3, 8.6, and 17.2 μg cadmium (as CdCl 2 )/ml of drinking water for 39 weeks. During the latter part of this period systolic blood pressure was measured, and water intake was monitored during the entire experimentation period. It was found that females ingested about as much water and therefore cadmium as did males, which resulted in higher intake of Cd/100 g body wt in females. Cadmium concentrations were higher in all organs of females than in males, and the increase was dose related in both sexes. Zinc and copper were elevated in kidneys, but only zinc in liver of both sexes. Blood pressure was elevated in males in a dose-dependent fashion, but was not changed in females. There were a number of other parameters which showed marked sex differences. These differences are discussed in the light of the greater intake, absorption, and retention of cadmium by females. Suggestions of biochemical changes related to cadmium-induced hypertension are also examined.

Copper deficiency effects on cardiovascular system and lipid metabolism in the rat; the role of dietary proteins and excessive zinc

Weanling rats were fed a copper-deficient purified diet. The effects of varying the type of protein and supplements of copper and zinc on cardiovascular pathology and some biochemical parameters were investigated. It was found that cardiomyopathy developed in the copper-deficient groups. Milk powder caused significant exacerbation of this development relative to dietary casein or egg white. Angiopathy developed only when dietary zinc was 20 ppm. Dietary copper did not change this situation. Serum cholesterol was elevated when copper was low and casein or milk powder were the protein source. The data point to an interaction between type of protein and dietary copper or zinc in the pathogenesis of cardiovascular lesions.