19b) Iron Flashcards
how is free iron toxic?
participates in chemical reactions that generate free radicals
iron compartments
Hemoglobin (majority)
Tissue iron
Myoglobin
A labile pool
men: —- g iron
women: —- g iron
4
2-3
Most iron from diet is in the ——– state (Fe–), but it needs to be in the ——– state (Fe–) to be absorbed.
ferric - 3+
ferrous - 2+
dietary iron is reduced by…
vitamin C or ferric reductases present in the intestinal epithelium
Fe— is bound to transferrin
3+
2 binding sites of transferrin
for Fe3+
for bicarbonate
transferrin SPEP
B1 globulin
function of transferrin cycle
move Fe from outside the cell to inside
Transferrin binds to the ———– and becomes part of the interior of the cell
transferrin captor cells/receptors
Formed when ferritin is denatured by secondary lysosomes
hemosiderin
Outer shell of ferritin is composed of…
Interior is composed of…
apoferritin
ferric oxyhydroxide [Fe(OH)3] crystalline core
Has a higher iron concentration than ferritin, but it releases iron more slowly.
hemosiderin
Fe predominantly in the cells of the liver, spleen, and bone marrow
hemosiderin
Elevated in pts with rheumatoid arthritis, renal disease, heart disease, lymphomas, leukemia, and patients with iron storage disorder
ferritin
measured by immunochemical methods
ferritin
negative acute-phase reactant protein
concentrations will be decreased in inflammation or malignancy.
transferrin
serum transferrin =
0.007 x TIBC (ug/dL)
iron sat % =
100(serum iron/TIBC)
normal transferrin %sat
<45%
usually about 33%
serum iron method
spectrophotometry
Serum iron concentration reflects the Fe3+ bound to serum transferrin, does not include…
the iron contained in serum as free hemoglobin
serum iron measurement steps (3)
- Releasing iron from transferrin using an acid
- Reduction of Fe3+ ions to Fe2+ ions using ascorbic acid
- Reaction of the Fe2+ ions with a chromogen to give a colored complex
Bathophenanthroline
Ferrozine
Tripyridyl triazine
chromogens used to measure serum iron
TIBC =
serum iron + UIBC
max iron concentration that transferrin can bind
TIBC
steps to determine UIBC
- adding sufficient Fe3+ to saturate iron binding sites on transferrin
- excess is removed by adsorption with a compound (magnesium carbonate or sodium hydrogen carbonate)
- assay for iron content is then repeated
factors that affect iron profile
Diurnal variation
Menstruation
Pregnancy
Ingestion of iron
Progesterone-like oral contraceptives
Hepatitis
Acute and chronic inflammation
Iron overload without associated tissue injury
hemosiderosis
Genetic condition in which the body accumulates excess amounts of iron
hereditary hemochromatosis
HH triad
Bronzing of the skin
Cirrhosis
Diabetes
also – cardiomyopathies, arrhythmias, endocrine deficiencies
Linked to HLA loci on chromosome 6
HH
hemachromatosis dietary recommendations
- Reduction of red meats or organ meat
- Avoid iron supplements and alcohol consumption
- Avoid Vitamin C because they tend to increase intestinal iron absorption
