Gastrointestinal tract cadmium

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. 

Severe illness and death can occur from exposure to many cadmium compounds. It is absorbed in the gastrointestinal tract. However, it can be eliminated in the urine and feces in young, healthy people. 

Cadmium is poorly absorbed from the gastrointestinal tract whereas absorption from the respiratory tract appears to be more complete cigarette smokers may absorb 10 to 40% of inhaled cadmium. 5... 

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. 

Although copper is an essential element, it is much more toxic to cells than such nonessential elements as nickel and cadmium. Acute poisoning from ingestion of excessive amounts of copper salts, most frequently copper sulfate, results in nonspecific toxic-symptoms, a metallic taste, nausea, and vomiting (with vomitus possibly a blue-green color). The gastrointestinal tract can be damaged by ulceration. 

Saliva is not an important route of excretion since most of the chemicals present in saliva will eventually reach the gastrointestinal tract to be reabsorbed or eliminated in the feces. The unbound fraction of several therapeutic drugs may diffuse passively from plasma into saliva. This provides a noninvasive means of indirectly monitoring plasma concentrations of drugs like lithium, phenytoin, and theophylline. Metals like lead, cadmium, and mercury are also present in saliva. 

In the infant, absorption from the gastrointestinal tract of an orally administered drug differs from that in adults. Certain toxicants are absorbed to a greater extent by the young than by the adult. For example, young children absorb four or five times more lead than adults and 20 times more cadmium. In both adults and infants, the rate and extent of drug absorption depend on the degree of ionization, which, in turn, is influenced by pH. Within the first... 

SuGAWARA N and Sugawara C (1987) Effect of oral selenium on cadmium absorption from the gastrointestinal tract. Trace Subst Environ Health 21 440-449. 

The earlierst reports of the carcinogenic effect of cadmium on man are from 1965 [91]. In workers exposed to the dust, carcinomas of the prostate and malignant processes in the gastrointestinal tract, kidneys, liver and lung were observed [92, 93]. Teratogenic effects are also reported for certain cadmium compounds (cadmium chloride, cadmium sulphate) [94]. 

The effects of chemicals can vary strongly, depending on the incorporation route. The acidic environment in some parts of the stomach and gastrointestinal tract (pH = l to 5) can cause hydrolysis-sensitive chemicals to be decomposed on oral incorporation. Chemical transformations can lead to more toxic or less toxic compounds. In the stomach, acidic compounds are preferentially absorbed, while the absorption of alkaline and lipophilic chemicals occurs particularly in the intestinal tract The body excretes chemicals which are not directly resorbed either in the stomach or in the intestinal tract so that a possibly available toxic property may not become effective, e.g., in the case of cadmium sulfide or barium sulfate. 

The primary routes of cadmium exposure are ingestion and inhalation with absorption of cadmium through the skin being negligible. Cigarette smoke is an important source of cadmium via inhalation. Absorption of cadmium occurs in the gastrointestinal tract (4-7% in adults) and in the lungs (15-30% in adults). 

For cadmium and mercury age related differences in gut retention were also obtained. In suckling rats about 70 per cent of the whole body radioactivity was in the gastrointestinal tract while only 15 per cent was found in the gut of older animals six days after oral administration of 203jjg and 5mcd (Kostial et al., 1980a). 

The continuous synthesis of cadmium-binding metallothionein in the liver and kidneys will lead to cadmium being trapped there, and thus elimination is very slow. It has been estimated that less than 0.01% of the body burden is excreted daily, to a large extent via urine (Friberg et al., 1974), but also via bile and the gastrointestinal tract, saliva, skin, sweat, etc. (Molin and Wester, 1976 Elinder et al., 1978a, b Langmyhr et al., 1979). 

The body content of cadmium increases with age. In the newborn, the total body content is less that l xg, increasing to about 15-20 mg in cin adult human in the UK and Sweden. Cadmium enters the body mainly via the respiratory and gastrointestinal tracts. According to experimental data, after inhalation about 10-40% is absorbed. The absorption depends on the particle size and solubility, with higher values for small and highly soluble particles. ... 

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