Hematology Iron Kinetics Lecture

Iron

Most important metal for metabolic processes including energy production by cells and carrying oxygen

>2.5 grams

The amount of iron the average man has.

65%

The amount of iron in hemoglobin

25%

The amount of iron used for storage in the body

10%

The amount of iron found in other locations in the body

Functional iron

Found within cells, such as hemoglobin, myoglobin, sulfur-iron clusters, enzymes and cytochromes

Storage iron

Not currently functional but is ready for use (hepatocytes and macrophages)

Transport iron

Moving from one site to another in plasma

Fenton Reaction

When ferrous iron can react with peroxide to form highly reactive molecules

Fenton Reaction

Fe2+ + HO-OH → ●Fe3+ + HO- + ●OH

Chaperone proteins

Proteins that carry ferric iron (Fe3+), then proteins on membrane reduce to Ferrous (Fe2+) before membrane transit

Ferric Iron

Fe3+

Ferrous Iron

Fe2+

Small intestines

The organ where iron is absorbed as ferritin

Ferritin Absorption

Enterocytes absorb ferritin (heme & Ionic)

Endocytosis

The transport of substances into the cell by engulfing them in a vesicle formed by the plasma membrane

Macropinocytosis

Form of endocytosis characterized by the nonspecific internalization of large amounts of extracellular fluid

Heme absorption

Heme carrier protein 1 (HCP1) in luminal membrane of enterocytes allows heme absorption via receptor-mediated endocytosis

Ionic iron absorption

Non heme ionic iron in Fe3+ must be reduced by duodenal cytochrome b prior to entering enterocyte then carried across luminal membrane by divalent metal transporter 1 (DMT1)

Ferroportin

Only known protein that exports iron across cell membranes

Apotransferrin (ApoTf)

Carries oxidized iron

Transferrin (Tf)

The iron clad molecule

Eyrthrocyte Iron Sensing & Hepcidin Production

RBC secrete erythroferrone (ERFE) that sequesters BMPs in turn iron absorption and recycling increases to promote availability of iron for Hgb production

Cellular Iron Acquisition

Cells regulate how much iron they can absorb with specific carriers working for receptor-medicated endocytosis

Cellular Iron Storage

Cells can store iron in case of new iron decline; storred in apoferritin

Red meats, legumes, and dark green leafy vegetables

Foods high in iron

10-20mg

The amount of iron that is recommended for intake

Myoglobin of muscles and hemoglobin in blood

The most bioavailable source of dietary iron

Serum iron

Screening test

Total Iron-binding capacity (TIBC)

Screening test

Percent transferring saturation

Screening test

Serum Ferritin

Screening test

50-160 ug/dL

The amount of serum iron in an adult male

250-400 ug/dL

The total amount of iron that could be transported in the plasma in adult males

20-55%

The percentage of transferring iron-binding sites that are occupied by iron

Prussian Blue Staining

A visual qualitative assessment of tissue iron stores