Iron Distribution and Compartments
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Questions and Answers

What is the largest percentage of body iron found in?

Hemoglobin in red blood cells

Where is the 20% of body iron stored?

In hepatocytes and macrophages in the spleen and bone marrow

What is the functional compartment of iron kinetics?

Iron functioning within cells, e.g. hemoglobin, myoglobin, and cytochromes

What is the storage compartment of iron kinetics?

<p>Iron stored in macrophages and hepatocytes, available when needed</p> Signup and view all the answers

What is the transport compartment of iron kinetics?

<p>Iron in transit from one body site to another</p> Signup and view all the answers

What percentage of body iron is divided among muscles, cytochromes, enzymes, and plasma?

<p>10%</p> Signup and view all the answers

Where is myoglobin found?

<p>In muscles</p> Signup and view all the answers

What is the role of the storage compartment?

<p>To hold iron available for use when needed</p> Signup and view all the answers

What is the largest source of recycled iron in the body?

<p>Red blood cells</p> Signup and view all the answers

Where do senescent red blood cells get ingested?

<p>Spleen</p> Signup and view all the answers

What molecule enables macrophages to export iron?

<p>Ferroportin</p> Signup and view all the answers

What binds to exported iron?

<p>Apotransferrin</p> Signup and view all the answers

In what forms can iron be absorbed?

<p>Ionic iron or nonionic iron</p> Signup and view all the answers

What type of foods are high in iron?

<p>Red meats, legumes, and dark green leafy vegetables</p> Signup and view all the answers

Why is iron recycling important?

<p>To meet the body's iron demand</p> Signup and view all the answers

What is the purpose of iron regulation in the body?

<p>To maintain optimal iron levels</p> Signup and view all the answers

What does haptoglobin bind to?

<p>hemoglobin</p> Signup and view all the answers

What is the average amount of iron absorbed from the US diet?

<p>1 to 2 mg</p> Signup and view all the answers

What does hemopexin bind to?

<p>heme</p> Signup and view all the answers

Why are haptoglobin and hemopexin unable to pass through the glomerulus?

<p>because they are proteins</p> Signup and view all the answers

What is the purpose of collecting a fasting specimen for serum iron?

<p>to measure highest levels</p> Signup and view all the answers

What does serum iron indicate?

<p>available transport iron</p> Signup and view all the answers

What type of cells mediate the haptoglobin-hemoglobin complex?

<p>macrophages</p> Signup and view all the answers

What type of cells mediate the hemopexin-heme complex?

<p>hepatocytes</p> Signup and view all the answers

What is the total iron-binding capacity an indicator of?

<p>transferrin level</p> Signup and view all the answers

What is calculated as a percentage of serum iron to total iron-binding capacity?

<p>percent transferrin saturation</p> Signup and view all the answers

What is the gold standard for assessing body iron stores?

<p>Prussian blue staining</p> Signup and view all the answers

What accumulates in red blood cells when iron is not incorporated into heme?

<p>zinc protoporphyrin</p> Signup and view all the answers

What is the consequence of impaired ferrochelatase, such as in lead poisoning?

<p>zinc protoporphyrin accumulation</p> Signup and view all the answers

What is the relationship between serum iron and TIBC in calculating percent transferrin saturation?

<p>serum iron is divided by TIBC</p> Signup and view all the answers

What is the primary function of transferrin?

<p>iron transport</p> Signup and view all the answers

What is the purpose of Prussian blue staining?

<p>assessing tissue iron stores</p> Signup and view all the answers

What is ferritin an indicator of in the body?

<p>iron stores</p> Signup and view all the answers

What is the limitation of using ferritin as an indicator of iron stores?

<p>it may be falsely increased during an infection or inflammation</p> Signup and view all the answers

What is the soluble transferrin receptor an indicator of?

<p>functional iron available in cells</p> Signup and view all the answers

How does the level of soluble transferrin receptor relate to the number of TfR1 on the membrane?

<p>it is inversely proportional</p> Signup and view all the answers

What is the role of ferritin during an infection or inflammation?

<p>it attempts to horde all iron away from bacteria</p> Signup and view all the answers

Why is ferritin not a perfect indicator of iron stores?

<p>it can be affected by infections or inflammation</p> Signup and view all the answers

What is the relationship between serum ferritin levels and stored iron in the body?

<p>they are highly correlated</p> Signup and view all the answers

What is the significance of TfR1 on the membrane in relation to iron availability?

<p>it indicates the availability of functional iron in cells</p> Signup and view all the answers

Study Notes

Iron Distribution

  • 70% of body iron is found in hemoglobin in red blood cells
  • 20% is stored in hepatocytes and macrophages in the spleen and bone marrow
  • 10% is distributed among muscles, cytochromes, and various iron-containing enzymes, and plasma

Iron Compartments

  • Functional compartment: iron functioning within cells (e.g., hemoglobin, myoglobin, cytochromes)
  • Storage compartment: iron stored in macrophages and hepatocytes
  • Transport compartment: iron in transit from one body site to another

Iron Absorption

  • Iron can be absorbed as either ionic or nonionic iron
  • High levels of iron are found in red meats, legumes, and dark green leafy vegetables
  • Bioavailability: 1-2 mg of iron is absorbed in the US diet, adequate for most men, but not for menstruating women, pregnant and lactating women, and growing children

Iron Transport

  • Iron is transported in the blood bound to apotransferrin
  • Haptoglobin binds to hemoglobin, mediated by macrophages with haptoglobin-hemoglobin receptor
  • Hemopexin binds to heme, mediated by hepatocytes with hemopexin-heme receptor and ferroportin

Iron Recycling

  • Largest percentage of recycled iron comes from senescent red blood cells
  • Macrophages ingest senescent red blood cells and export iron bound to apotransferrin

Laboratory Assessment of Body Iron Status

  • Serum Iron: indicator of available transport iron
  • Total Iron-Binding Capacity (TIBC): indirect indicator of transferrin level
  • Percent Transferrin Saturation: indirect indicator of transport iron and transferrin level
  • Prussian Blue Staining: visual qualitative assessment of tissue iron stores
  • Zinc Protoporphyrin (ZPP): indicator of functional iron available in red blood cells
  • Ferritin: indicator of iron stores
  • Soluble Transferrin Receptor (sTfR): indicator of functional iron available in cells

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Description

Learn about the distribution of iron in the body, including its functional, storage, and transport compartments. Understand the percentage of iron found in different parts of the body.

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