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 Professor Paula Drosescu MD PhD
Societatea Romana de Medicina Sportiva

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The Metabolism of Selenium

The metabolism of selenium is well – known, even though several characteristics make it difficult to understand:
 - this metalloid is introduced in the human body with the help of aliments in different chemical forms;
 - chemically speaking, selenium resembles sulphur very much, and therefore it will sometimes be able to use the enzymatic or transport systems of the latter.
The absorption of selenium depends on the form it is found in, and it is performed, at a faster or a slower rate, in the small intestine. Selenites and selenates are absorbed first during the intestinal digestion (in the duodenum), whereas the organic selenium (selenium methitonine) is absorbed later (in the ileon, the site of the small molecular chain peptides). The organic forms of selenium are better absorbed than the inorganic (mineral) ones. The transport of selenium in the plasma is nonspecific, selenium being usually bound to a an b globulins and to albumin. Selenium is stored in the skeletal muscles, in the liver and in the kidneys. It is eliminated in the urine (60%), feces (35%), and very little through perspiration. The pulmonary elimination of selenium is accompanied by a characteristic breath that has the odor of garlic is always the sign of selenium excess intoxication.

The Biological Effects of Selenium

The action against free radicals. Selenium is a component of a human protein, formed of four identical subunits, each subunit including a selenium atom in the form of selenium cysteine. This protein, containing selenium, is part of the glutathione peroxidase structure, one of the most efficient enzymes to fight free radicals excess. This discovery was made in 1971 by Rotruck. Selenium cysteine is a selenium – amino acid in which selenium has taken the place of sulphur. The amino acid that contains sulphur is called cysteine.
The seleno – aminic acids are a family of alpha – aminated acids , analogs of the metilcysteine, methionine, cysteine and cystathyonine, in which sulphur has been replaced by selenium. They can be found in the plants that grow on the selenipherous soils. They are antagonists of the sulphur amino acids. In cattle seleno – aminic acids cause, among others, the specific manifestations of selenium poisoning. Selenium cystationine causes various digestive disturbances. The main selenium – aminic acids are: selenium – cystationine, selenium – cysteine, selenium – methyonine. In furry animals, the selenium acids excess causes “atrichia”, a genetic disorder characterized by absence of hair. By means of analogy, one can ask: could selenium excess in the human body cause baldness?
Glutathione peroxidase seems to be the only selenoenzyme known in the human body. This enzyme is not only an important defending biomolecule, but also a compensating system against the oxidative danger of intracellular molecules, with small molecular masses: proteins, poliunsaturated fatty acids. Neve, while studying the biological functions of selenium, found in 1988 that the aggressions that occur during normal metabolic processes or during some pathological circumstances ( inflammation, arterial sclerosis, cancer, degenerative disorders, cellular ageing, etc.) are connected to the free radicals and the dangers they carry with them. Even the slightest selenium deficiency impairs the activity of glutathione peroxidase and leads to the peroxidation of cellular and intracellular membranes. The cellular permeability is disturbed, and numerous biomolecules, such as DNA, continue to work, but due to those anomalies the genetic code is changed. This is a risk, or at least a plausible cause of cancer. The aggression caused by the selenium deficiency causes specific clinical syndromes, such as: hemolysis, tissue necrosis, degenerative disturbances, and, as a consequence, the risk of chronic diseases increases.

next page ...   → The Role of Glutathione Peroxidase in the Metabolism of Prostaglandins
                         The Disintoxication Action of Selenium
Professor Paula Drosescu, MD. PhD
Faculty of Physical Education and Sports
“Al. I. Cuza” University Iasi
December 2, 2009
Medical Cabinet Alternative Iasi
Associate Certified Coach ICF

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