Se 3 pp - 1 Selenium Selenium 2011 Selenium History •...

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Unformatted text preview: 1 Selenium Selenium 2011 Selenium History • 1957 Schwarz and Foltz – dietary Se prevents liver necrosis in rats fed Se deficient diet also deficient in Vit E Selenium History • Proof that Se essential for animals • Widespread use of Se animal feeds – eliminated animal diseases • due to Se deficiency 2 Selenium History • 1960-1970’s Research – Se has anticarcinogenic activity • Discovery of glutathione peroxidase – Se metalloenzyme Selenium: Dietary Sources • Good sources: – fish, seafood, eggs, meat, vegetables • Foods vary depending on – where plant is grown where plant is grown – where animal raised • Se content of meat reflects – Se in diet supplements – livestock in US supplemented with inorganic Se Selenium Distribution in the US 3 Types of Selenium Types of Selenium • Inorganic and organic forms, and both are present in the body. Inorganic •Selenite (SeO 3 2- ) •Selenate (SeO 4 2- ) •Selenide (HSe- ) Organic •Selenocysteine (Sec) •Selenomethionine Absorption Absorption • Selenomethionine- and selenocysteine- containing proteins: – Selenoamino acids absorbed intact by animals and humans animals and humans – As high as 98% • Inorganic Se forms: – Absorption ~85% Fig. 12-15, p. 507 4 Intestinal Transport Intestinal Transport • Luminal and basolateral inorganic Se transporters: – None have been described, different from other minerals other minerals. • Selenomethionine and methionine transported the same. • Se absorption rate does not increase in deficiency. (Liuzzi et al., PNAS 2004) Body Composition Body Composition • Total body Se ≈ 30 mg • Tissues: – Kidney greatest Se concentration 0.6-1.8 μ g/g – Others liver > RBCs > muscle > spleen > pancreas – Muscle = largest Se mass Blood Levels and Excretion Blood Levels and Excretion • Blood levels in the U.S. population – 125 μ g/ L • China = 15 μ g/ L • Excretion: – Methylselenol: major urinary form – Urinary excretion important for maintaining homeostasis (i.e., urinary Se decreases when in limited supply) 5 Fig. 12-16, p. 508 Metabolism Metabolism • Catabolism of selenomethionine or selenocysteine releases inorganic Selenide (HSe- )....
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Se 3 pp - 1 Selenium Selenium 2011 Selenium History •...

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