Iron physiology Flashcards
what is Ferrous iron and can you absorb it?
Fe2+
-absorbable iron
What is Ferric iron and can you absorb it?
Fe3+
-not absorbable
what form is iron in when digested?
Fe3+
-ferric
-not absorbable
where does iron absorption occur?
duodenum
what enhances absorption of iron?
-Ascorbic acid
-Alcohol
-Haem (from meat) iron easier to absorb than non haem
what inhibits absorption of iron?
-Calcium
-Tannins e.g. tea
-Phytates e.g. cereals, bran, nuts and seeds
where are Duodenal cytochrome B found?
luminal surface of duodenum
role of Duodenal cytochrome B?
reduced ferric (Fe3+) iron to ferrous (Fe2+) form
what transports ferrous iron into the duodenal erythrocyte?
DMT-1
-divalent metal transporter 1
role of ferroportin?
-facilitates iron export from the enterocyte
-passed on to transferrin to transport elsewhere
what is the major negative regulator of iron uptake?
Hepcidin
where is hepcidin produced?
-in the liver
how does Hepcidin work?
-Major negative regulator of iron uptake
-Produced in liver in response to increased iron load and inflammation
-Bind to ferroportin and causes its degredation
-Iron therefore ‘trapped’ in duodenal cells and macrophages
-Hepcidin levels decrease when iron deficient
what is apotransferrin?
transferrin not bound to anything
explain the mechanism of how non haem iron is taken up?
- Iron digested and presents in Fe3+
- Fe3+ converted to Fe2+ by duodenal cytochrome B on the lumen of duodenum
- Fe2+ and H+ transported into the duodenal enterocyte by DMV-1 (divalent metal transporter 1)
- Some iron is stored as ferritin
- Fe2+ leaves the cell through ferroportin
- Hephaestin converts Fe2+ to Fe3+ (Iron needs to be in Fe3+ form to travel)
- Transferrin binds to Fe3+ and allows it to travel through the body
75% transferrin goes to bone marrow for erythropoieisis, they bind to tranferrin receptors on RBC
10-20% taken to the liver and stored as ferritin in the liver
