Tellurium excretion

Tellurium excretion patterns depend on the chemical forms and mode of administration of the compounds. Parenterally administered tellurium is excreted mainly in the urine rather than the feces, whereas orally ingested tellurium salts are excreted mainly in the feces (Durbin 1960). After oral dosing to rats, 60 -80% of ingested tellurite is rapidly excreted in the feces. The absorbed tellurium is secreted in the bile and enters the intestine. Small amounts of absorbed elemental tellurium and tellurite are exhaled ( 0.1%) presumably as dime-thyltelluride, and produce a characteristic garlic-like breath odor (De Meio 1946). 

Slouka V (1970) Distribution and excretion of intravenous radio tellurium in the rat. Sb Ved Pr VLVDU Hradci Kralove 47 3-19. 

In the form of CdS Sei selenium is used as a red pigment in glass and ceramics. Below its melting point, Se is a semiconductor. Tellurium is used as an additive (<0.1%) to low-carbon steels in order to improve the machine qualities of the metal. This accounts for about half of the world s consumption of tellurium. Catalytic applications are also important, and other applications stem from its semiconducting properties, e.g. cadmium telluride has recently been incorporated into solar cells (see Box 14.3). However, uses of Te are limited, partly because Te compounds are readily absorbed by the body and excreted in the breath and perspiration as foul-smelling organic derivatives. 

There is no quantitative information on the respiratory absorption of tellurium compounds in humans. In animal experiments elemental tellurium and tellurium dioxide was very poorly absorbed from the gastrointestinal tract, but about 25% of ingested water-soluble tellurites and tellurates were absorbed and distributed in tissues [S]. Absorption of tellurium in the alimentary canal is finished within 2 hr. In rats [6] absorption occurs mainly in the duodenum and jejunum. The absorption is estimated as 10-25%. The injected tellurium in rats quickly spreads throughout the body, and 60-80% of tellurium is excreted by the kidney [5]. After the intake of tellurium, 90% is bound to erythrocytes and most of the rest to plasma proteins [7]. Organic tellurium esters may be absorbed through the intact skin [8]. 

A number of other selenium proteins have been discovered in biological materials, but their function is not yet sufficiently known. For example, a selenium protein (17kDa) was found in rat sperm. It is interesting that high concentrations of selenium in male sexual organs are maintained in animals with selenium deficiency therefore, selenium compounds are likely to be important for reproductive function. Some anticarcinogenic effects are also attributed to this element. Selenium also reduces the toxic effects of arsenic, cadmium, mercury, thallium and tellurium. With arsenic, the mechanism of this protective effect is the formation of selenobis(S-glutathionyl)arsinium anion, which is formed in erythrocytes and excreted in bile (6-36). 

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