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Abstract
Selenium is an essential trace element important in many biochemical and physiological processes including the biosynthesis of a component of mitochondrial electron transport systems , regulation of ion fluxes across membranes ,maintenance of the integrity of keratins ,stimulation of antibody synthesis ,and activation of glutathione peroxidase (an enzyme involved in preventing oxidative damage to cells. Selenium has both nutritional function and toxicity according to its concentration. In recent years selenium deficiency in domesticated animals ,usually interrelated with a concomitant vitamin E deficiency ,has become a problem in many areas of the world resulting in serious economic losses .Consequently Selenium supplementation of animal foodstuffs have been extensively adopted in order to supply nutritionally adequate amounts of selenium to livestock .Selenium has been recently recognized as an essential trace element also for man and several selenium-dependent syndromes ,including Keshan-disease, a cardiomyotathy, have been reported . Selenium – containing commercial preparations ,mainly tablets have thus become freely available also to humans .Owing to the well known toxic properties of the element, however , the risk deriving from misuse and /Or abuse of selenium should not be underestimated .Experimental chronic selenium in animals affects some major organs ,including the liver spleen