iron kinetics

It is critical to energy production in all cells, being at the center of the cytochromes of mitochondria.

IROn

where does iron come from

diet or stored in the body

The largest percentage of body iron, nearly 70% of it, is held

within the hemoglobin

whereas almost 20% of body iron is in storage, mostly within

macrophages and macrophages in the spleen and bone marrow

what cells absorbed iron from dietary sources

enterocytes

before iron is absorbed in enterocytes they must be reduced by ____

cytochrome duodenal b

once iron is absorbed by enterocytes it must be

carried to luminal cyte by divalent metal transporter 1

The protein on the basolaminal side of the enterocyte that exports ferrous iron into the blood, thus truly absorbing it into the body,

is ferroportin.

a protein able to bind to ferroportin, leading to its inactivation.9 As a result, iron absorption into the body decreases.

hepcidin

When the body has adequate stores of iron, the hepatocytes sense that and will increase production of

hepcidin

what form must iron be for transport in blood

ferrous

a protein on the basolaminal enterocyte membrane,is able to oxidize iron as it exits the enterocyte.

hephaestin

Once oxidized,the iron is ready for plasma transport, carried by a specific protein,

apotransferrin then once iron binds its transferrrin

Individual cells tightly regulate the amount of iron they absorb to minimize the adverse effects of free radicals. This is accomplished by relying on a specific carrier to move iron into the cell by a process called

receptor mediated endocytosis

How do individual cells, like erythroblasts, safely acquire iron from the blood?

Through receptor-mediated endocytosis. They use a receptor (TfR1) on their membrane to bind iron-loaded transferrin from the blood, pull it inside in a vesicle (endosome), and then release the iron in the acidic environment of the endosome.

What is the specific mechanism that allows an erythroblast to get the massive amount of iron needed for hemoglobin?

kiss and run

After the iron is released inside the cell, what happens to the transferrin protein and its receptor (TfR1)?

endosome recycles them

Ferric iron is stored in a cage-like protein call

apoferritin once iron bind (ferritin)

Ferritin iron can be mobilized for use during times of iron

need by lysosomal degradation of the protein.21 Partially

degraded ferritin is known as

hemosiderin

The largest percentage of recycled iron comes from

rbc

Senescent (aging) red blood cells are ingested by

macrophages in the spleen

are plasma proteins that salvage plasma hemoglobin or heme, respectively, freed during fragmentation hemolysis

haptoglobin and hemopexin

Foods containing high levels of iron includ

red meat legumes and green leafy vegetables

Indicator of available transport iron

serum iron level

serum iron level reagent

ferrozine

serum iron level adult male reference

50-160 ug/dl

specimen needed for serum iron level

fasting first morning

The amount of iron in plasma or serum will be limited by the

amount of transferrin that is available to carry it. measures transferrin

total iron binding capacity

total iron binding capacity reagent

magnesium carbonate powder

tibc male referrence

250-400 ug/dL

Indirect indicator of transport iron and transferrin level

percent transferring saturation

Percent Transferrin Saturation formular

si/tibc x 100%

pts male referrence

20 to 55%

Measured by immunoassay. Correlates highly with stored iron

(assessed by Prussian blue staining of bone marrow)

serum ferritin level principle

is considered the gold standard for assessment of body iron stores.

prussian blue stain

Indicator of functional iron available in cells.

soluble transferrin receptor level

Soluble Transferrin Receptor (sTfR) Level Principle

Cells increase TfR1 expression on their membrane when intracellular iron drops. A truncated form of this receptor is shed into the plasma and can bedetected by immunoassay.

Indicator of functional iron available in developing red blood cells

hemoglobin content of reticuloctyes

Indicator of functional iron available in red blood cells.

zinc protporphyrin levels

Improves the identification of iron deficiency when individual assay values are equivocal. Since sTfR rises and ferritin drops in iron deficiency, the ratio amplifies these changes.

stfr/log ferritin index

A four-quadrant plot that graphs the sTfR/log ferritin index against

the hemoglobin content of reticulocytes.

thomas plot