Changes

==1. What is Selenium?==

==1. What is Selenium?==

Selenium is a trace element that, like iodine, is required in only very small quantities. Chemically it is classified as a semi-metal or metalloid element and can exist in four oxidation states: 2-, 0, 4+ and 6+. This accounts for its existence in several different forms in nature, e.g. as 4+ in sodium selenite (Na₂SeO₃), 6+ in sodium selenate (Na₂SeO₄) and 2- in selenocysteine.

Selenium is a trace element that, like [[Iodine - Nutrition|iodine]], is required in only very small quantities. Chemically it is classified as a semi-metal or metalloid element and can exist in four oxidation states: 2-, 0, 4+ and 6+. This accounts for its existence in several different forms in nature, e.g. as 4+ in sodium selenite (Na₂SeO₃), 6+ in sodium selenate (Na₂SeO₄) and 2- in selenocysteine.

==2. Why is it Important?==

==2. Why is it Important?==

==3. Roles in the Body==

==3. Roles in the Body==

There is little direct information on the metabolism of selenium in dogs and cats but studies in other mammals, including man, show that after absorption selenium is taken up by red blood cells then released into the plasma where it is bound to albumin and transported to the tissues. In all the selenium-containing enzymes selenium exists as selenocysteine, which can be formed from selenomethionine by the same metabolic pathways that convert methionine to cysteine. Selenium is a component of deiodinase enzymes responsible for the conversion of thyroxine to tri-iodothyronine, the active form of thyroid hormone [WikiVet Link to Iodine]. Selenium-containing proteins have been reported to support the immune response and protect against certain cancers. There is also some evidence that selenium may be protective against the adverse effects of mercury in cats, perhaps by inhibiting its absorption<ref>Houpt, K, Essick, L, Shaw, E, Alo, D, Gilmartin, J, Gutenmann, W, Littman, C, Lisk, D (1988). “A tuna fish diet influences cat behaviour”. J. Toxicol. Environ. Health 24:161-172.</ref>. Urine is the primary excretion route for selenium and the major urinary metabolite is selenosugar B, a compound of selenium and galactosamine<ref>Suzuki, K (2005). “Metabolomics of selenium: Se metabolites based on speciation studies”. J. Health Sci. 51:107-114.</ref>.

There is little direct information on the metabolism of selenium in dogs and cats but studies in other mammals, including man, show that after absorption selenium is taken up by red blood cells then released into the plasma where it is bound to albumin and transported to the tissues. In all the selenium-containing enzymes selenium exists as selenocysteine, which can be formed from selenomethionine by the same metabolic pathways that convert [[Methionine and Cysteine - Nutrition|methionine to cysteine]]. Selenium is a component of deiodinase enzymes responsible for the conversion of thyroxine to tri-iodothyronine, the active form of [[Iodine - Nutrition|thyroid hormone]]. Selenium-containing proteins have been reported to support the immune response and protect against certain cancers. There is also some evidence that selenium may be protective against the adverse effects of mercury in cats, perhaps by inhibiting its absorption<ref>Houpt, K, Essick, L, Shaw, E, Alo, D, Gilmartin, J, Gutenmann, W, Littman, C, Lisk, D (1988). “A tuna fish diet influences cat behaviour”. J. Toxicol. Environ. Health 24:161-172.</ref>. Urine is the primary excretion route for selenium and the major urinary metabolite is selenosugar B, a compound of selenium and galactosamine<ref>Suzuki, K (2005). “Metabolomics of selenium: Se metabolites based on speciation studies”. J. Health Sci. 51:107-114.</ref>.

==4. Consequences of Selenium Deficiency==

==4. Consequences of Selenium Deficiency==