Cadmium calcium absorption

Human food, both plant and animal, usually contains satisfactory amounts of zinc to cover the requirement for this metal, which is present within the range of few to several pg per g of product. Zinc deficiencies are usually caused by a reduction of its absorption in the gastrointestinal tract rather than by its lack. Reduction in absorption may be caused by antagonistic activity of cadmium, calcium or phytates. A decrease in assimilation of zinc is also observed among alcoholics. 

After ingestion, an absorption of about 2% has been found in animals, " whereas an average absorption of about 6% was noted in five human beings given single doses of radioactive cadmium. Calcium, iron, or protein deficiency increases the retention rate. ""... 

In mammals, cadmium inhibits copper absorption across the intestinal mucosa (Aaseth and Norseth 1986). Intercorrelations of copper with cadmium and zinc in livers of polar bears (Ursus maritimus) are probably mediated by metallothioneins, which may contain all three metals (Braune etal. 1991). In rats, copper protects against nephrotoxicity induced by cadmium, provided that copper is administered 24 h prior to cadmium insult. Specifically, rats given 12.5 mg Cu/kg BW by way of subcutaneous injection 24 h before receiving 0.4 mg Cd/kg BW — when compared to a group receiving Cd alone — did not have excessive calcium in urine and renal cortex or excessive protein in urine. Thus, 2.8 mg Cu/kg BW protects against 0.25 mg Cd/kg BW (Liu et al. 1992). 

Cadmium is a widely distributed metal used in manufacturing and is present in a number of consumer products. Dietary exposure to cadmium is possible from shellfish and plants grown on cadmium-contaminated soils. Absorption is increased when associated with low levels of iron or calcium in the diet. Some plants, such as tobacco, can concentrate cadmium from even low levels in the soil. The lung readily absorbs cadmium, thus cigarette smokers have elevated cadmium exposure. Cadmium is also used as a metal alloy, in paint, and in batteries (Ni-Cad, nickel-cadmium). Workplace exposure can occur in welding and battery manufacture. 

Because of the toxicity of cadmium, its use was abandoned in the 1980 s. Nevertheless, by improving the quality of the raw materials and changing the reaction stoichiometry, it was possible to reproduce the quantum yield of the halophosphates, even without the addition of cadmium [5.373]. The absorption of the exciting UV radiation is strongly dependent on the particle size of halophosphate phosphors and decreases rapidly for particles larger than 3 pm. The particle size is influenced to some extent by the particle size of raw materials (calcium hydrogen phosphate) in the firing mixture. Mechanical separation processes (sieves) are used to free the fired product from undesired coarse and fine particles. 

The BS I lectin requires bound calcium for activity.131 Two moles of calcium and 1.25 moles of magnesium per mole of protein were found by atomic absorption spectroscopy. Inactive, metal-free lectin, obtained by exhaustive dialysis, could be reconstituted by addition of calcium, cadmium, or strontium (magnesium restored 80% of the activity). Although bound-calcium was not removed by dialysis against EDTA, inclusion of this chelating agent in the precipitin reaction resulted in complete inhibition. 

Gastrointestinal absorption, and subsequent utilization and retention by the body, of essential trace elements such as zinc, copper, and selenium can also be enhanced or diminished by the presence or absence of other trace elements and chemicals in the diet (WHO, 1996). For example, cadmium and lead absorption is enhanced when dietetic intake of calcium, iron, and phosphate is low. Phytate, an organic phosphate that is abundant in diets high in unrefined grains, especially when accompanied by high dietetic calcium, helps suppress the uptake of potentially toxic elements such as lead and cadmium, but also inhibits the uptake of essential zinc (WHO, 1996). 

Atomic Absorption Spectrometry. Flame atomic absorption spectrometry was adopted as the second method of analysis and since low volumes of air were sampled, only a limited number of elements were detected in the collected particles (calcium, copper, iron, magnesium, and zinc). Aluminum, cadmium, chromium, cobalt, lead, manganese, and nickel were not detected in any of the samples. This resulted in a limited... 

The uptake of aluminum, cadmium, chromium, cobalt, cop-per, iron, lead, magnesium, manganese, molybdenum, nickel, silver, tin, and zinc by B. subtilis Strain 168 is reported. These data were obtained during the lag phase, exponential phase, stationary phase, and the sporulation phase of the maturation cycle of this bacterial strain. Nonflame atomic absorption spectrometry was the method of analysis for all the metals except calcium, which was determined by flame atomic absorption spectrometry. The complete microbiological and analytical procedures are described. Uptake curves as a function of moles per cell, of moles per dry weight of a cell, and of percent available are reported. The data show that these metals seem to be required for growth. No attempts were made to postulate the roles played by these metals. 

Absorption of cadmium in the gastrointestinal tract is 4-7% in adults absorption is probably higher in children. Diets low in calcium, iron, and protein enhance cadmium absorption. Zinc is an antagonist to cadmium (decreases cadmium absorption). Cadmium absorption by the lungs is dependent on particle size and the solubility of the cadmium compound, but is generally between 15% and 30%. Dermal absorption of cadmium is insignificant. 

Since the kidneys are the main depot for cadmium, they are of greatest concern for cadmium toxicity. Cadmium interferes with the proximal tubule s reabsorption function. This leads to abnormal actions of uric acid, calcium, and phosphorus. Amino aciduria (amino acids in the urine) and glucosuria (glucose in the urine) result in later stages, proteinuria (protein in the urine) results. When this happens, it is assumed that there is a marked decrease in glomerular filtration. Long-term exposure to cadmium leads to anemia, which may result from cadmium interfering with iron absorption. 

Cadmium shows a very high bioconcentration factor (BCF), mainly because of its extremely slow elimination, although the absorption is rather low. The metal is not biomethylated and does not exist in any highly bioavailable organic forms. Its uptake is coupled to calcium and iron transporting mechanisms in which cadmium is mistaken for the essential metal and consequently transported. The uptake of cadmium is thus enhanced in situations of iron deficiency. 

Data concerning the toxicity of the four discussed toxic minerals are presented in Tables 4.5 and 4.6. The uptake of elements is not entirely independent of one another. Elements of similar chemical properties tend to be taken up together. Sometimes one element has an inhibiting effect on another, or there can be a synergistic effect, e.g., enhancement of absorption of calcium in the presence of adequate amounts of phosphorus, or cadmium and lead hindering calcium and iron absorption, or zinc and copper antagonism and their influence on the ratio of Zn/Cu on copper deficiency. 

Zinc is relatively nontoxic but, if present in the diet at high concentration and in readily available form, it can interfere with the absorption of calcium, copper, iron, and cadmium and can produce anemia. These elements, in turn, can decrease zinc absorption if present in sufficient quantities. Use of zinc salt lozenges has been claimed to reduce the duration of the common cold. However, many randomized, double-bind, placebo-controlled trials have failed to show any beneficial effects of zinc lozenges in reducing the duration of upper respiratory tract viral infections. 

He ZY, Li JC, Zhang HY, Ma M. Different effects of calcium and lanthanum on the expression of phytochelatin synthase gene and cadmium absorption in Lactuca sativa. Plant Sci 2005 168 309-18. 

The ASTM F 1185 designation specifies chemical and crystallographic requirements for hydroxyapatite applied to the surfaces of surgical implants. Elemental analyses for calcium and phosphorus will confirm the expected stoichiometry of hydroxyapatite. The calcium and phosphorus contents will be determined by a suitable method such as ion chromatography. A quantitative X-ray diffraction analysis will determine a hydroxyapatite content of at least 95%. The concentration of deleterious trace elements such as arsenic, cadmium, mercury and lead will be assessed for hydroxyapatite derived from natural resources. The analysis of other trace elements may be required, based on the conditions, apparatus or environments specific to the manufacturing techniques and raw materials. Inductively coupled plasma/mass spectroscopy (ICP/MS), atomic absorption (AAS) or the... 

Chemical analysis provides much more precise data about the sample, particularly the determination of metallic elements, mainly lead, cadmium, iron, calcium, sodium as well a.s anions, chlorides, fluorides, nitrates, carbonates and sulphates. The analyses are performed most frequently by spectrophotometry, atomic absorption spectrometry, or polarography in recent years radionuclide X-ray fluorescence and activation analysis have been used. 

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