4b - Iron metabolism and microcytic anaemias Flashcards
What is Microcytic anaemia?
- Reduced rate of haemoglobin synthesis
- Erythrocytes smaller than normal (microcytic)
- Cells often paler than normal (hypochromic) - not as red bc of less
- What causes Microcytic anaemia?
- Reduced haem synthesis
- Reduced globin chain synthesis: alpha or beta thalassaemia
Identify the full list of causes for Microcytic anaemic (hint: acronym - cats have t****)?
Describe some of the functions of iron
- Oxygen carriers: Haemoglobin in red cells; Myoglobin in myocytes
- Co-factor in many enzymes: Cytochromes (oxidative phosphorylation) Krebs cycle enzymes Cytochrome P450 enzymes (detoxification) Catalase
Why is the regulation of iron important?
- Free iron potentially very toxic to cells
- Complex regulatory systems to ensure the safe absorption, transportation & utilisation
- MOST IMPORTANT - Body has no mechanism for excreting iron
What two common oxidation states does iron exist in?
- Ferrous iron (Fe2+) - Reduced form. ABSORBED FORM
- Ferric iron (Fe3+) most common - Oxidised form.
What is dietary iron a mix of?
Haem iron (Fe2+) and non-haem (mixture of Fe2+ and Fe3+).
Identify some sources of haem and non haem iron
Where does the absorption of iron occur?
•duodeneum and upper jujenum
Describe the absorption of dietary iron
- Ingestion if iron in the haem form (meat) or non haem form
- Duodenum and upper jujenum - intestinal enterocytes – cells where our nutrients are absorbed from the gut BARRIER
- Chyme is the mixture of food leaving the stomach into the small intestine. Contain haem iron.
- Movement: Chyme –> Enterocyte –> Blood
- Food must be absorbed across our enterocyte to get them into the blood
- Haem can be absorbed by the intestinal enterocyte –> HAEM INSIDE OUR CELL
- Non haem composed of ferric and ferrous. Can only absorb ferrous (fe2+)
- So Fe3+ must be converted to Fe2+ - ferrous reductase works in combination with Vitamin c
- DMT 1 – Divalent metal transporter 1 - two charges – Fe2+ transport. Co transporter – when one iron comes in a H+ ion leaves
- Fe2+ once in the cell can be stored in the Fe 3+- linked to protein ferritin - function to store iron
- Ferroportin - allows Fe2+ to pass across the enterocyte into the blood
- Transferrin – transport molecule. Ferric ion. Two binds sites - can then be tansported around the body
Which factors positively affect the absorption of non-Haem iron from food?
- Vitamin C and citrate - prevent formation of inbsoluble iron compounds
- Vit C help reduces ferric to ferrous iron (works with ferric reductase)
Which factors negatively affect the absorption of non-Haem iron from food?
- Tannins (in tea) - found in tea. Combine non haem iron in the intestine. Reduces absorption of iron. Discourage anaemic patients from drinking tea.
- Phytates (e.g. Chapattis, pulses)
- Fibre
- Antacids (e.g. Gaviscon)
What is ferous reductase?
- Works in combination with Vitamin C
- Catalyses: Fe3+ –> Fe2+
- Found on the apical surfaces of enterocytes
What is DMT 1 – Divalent metal transporter 1?
- Located on the apical surface of intestinal enterocyte
- Co transporter - two charges – Fe2+ transport
- When one iron comes in a H+ ion leaves
What is Ferroportin?
- Found on the basolateral surface of the enterocyte
- Allows Fe2+ to pass across the enterocyte into the blood
What is Transferrin
- Transport molecule of ferric ion (Fe3+)
- Two binding sites for Fe3+ - can then be transported around the body
What are the two types of iron stores
- Functional
- Stored
What functional (available) iron is there?
- Haemoglobin (~2000 mg)
- Myoglobin (~300 mg)
- Enzymes e.g. cytochromes (~50 mg)
- Transported iron (in serum mainly in transferrin) (~3 mg)
Describe the mechanism of anaemia of chronic disease
