Selenium

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to explain an antioxidant function for selenium in relation to its role in glutathione peroxidase

Basics

  • An essential metal
  • functions as an antioxidant that works in conjunction with vitamin E
  • Several selenoproteins are involved in reducing oxidant stress:
  • Some effects are explained by its role in glutathione peroxidase in that its role overlaps that of vitamin E
  • Some forms of liver necrosis in rats can be cured by either selenium or vitamin E
  • 2 glut-SH + H2O2 = 2H2O + glut-S-S-glut
  • Many other effects remain to be explained in terms of Se-proteins
  • most Se is bound to proteins (Se-proteins)

Role

  • ~5-20 mg is present in the body
  • wide variation in intake 0.05-0.5 mg/day
  • Highest concentrations are in RBC, liver, spleen
  • Absorbed throughout the small intestine
  • Excreted:
    • in pancreatic secretions (enzymes)
    • across the gut wall
    • by kidney after metabolism

Toxicity

  • Selenium has a narrow window of effectiveness, above which toxic symptoms can ensue
  • Toxic effects in cattle and sheep in some countries ("blind staggers")
  • In humans, toxic effects include damage to liver and muscle but are rare
  • For toxicity, 25-50 times the RDI has to be consumed


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