Absorption of iron and gastrointestinal disease Flashcards
What is the role of iron in human biology?
Oxygen transport and storage
electron transport
plethora of enzymes
cell cycle control
Why is control of iron important?
There is no active excretory mechanism
Iron- physiological processing
very small amount of iron absorbed stored in the liver very small amount lost Iron circulates in plasma RBC made in bone marrow RBCs engulfed by macrophages haem broken down into bilirubin and ion is liberated
What is the purpose of Dcytb?
ferric reductase
What is DMT1?
divalent metal transporter responsible for ferrous uptake
What is Ferritin?
inert iron storage
What is the purpose of ferroportin?
Cellular iron efflux
What is hephaestin?
Ferroxidase
What is transferrrin?
essential for iron binding in blood
Why do patients who have had gastrectomies develop iron defieciency anaemia?
Acids can reduce Fe3+ to Fe2+- a form that is more readily absorbed in the duodenum. Removal of stomach often leads to decrease production of acid
Why is PPI used for hereditary haemochromatosis?
PPI decrease acid production. This decreases the reduction of Fe3+ to Fe2+ which is more readily abdorbed
How does non-enterocyte iron transport occur?
Transferrin receptor mediated endocytosis. Cells that are iron deficient would express more transferrin receptors on its cell surface
What does transferrin receptor mediated endocytosis involve?
Transferrin receptor, DMT-1 and the ferric reductase STEAP-3
How does haem transport occur?
Via HCP-1 at brush border of enterocyte
Once inside cell, what happens to haem?
Haem is broken down into haem-oxygenase -1 (HO-1). This releases free iron and biliverdin. Iron enters the labile iron pool within the cell and gets exported by ferroportin or stored by ferritin.
