Download - MLAB 2401: Clinical Chemistry Keri Brophy-Martinez Overview : Iron, Porphyrins, and Hemoglobin
MLAB 2401: Clinical MLAB 2401: Clinical ChemistryChemistryKeri Brophy-MartinezKeri Brophy-Martinez
Overview :Iron, Porphyrins, and Hemoglobin
Overview of IronOverview of IronEssential mineral to most living
organismsMost abundant trace elementWhere is it found?
◦Majority is found in red blood cells ◦Myoglobin: oxygen-carrying molecule
of muscle◦Tissue: bound to enzymes◦Bone marrow, spleen, liver: storage
forms
Where does iron come Where does iron come from?from?
• Two types• Heme• meats, especially
organ meats• Non-Heme• spinach, beets,
beans, almonds, bran flakes..etc
• Typical dietary intake is 10-20 mg per day.
Forms of IronForms of Iron• Ferrous(Fe2+)–Absorbed form
• Ferric (Fe3+)–Transport and storage form–Delivered to cells having receptor
sites• Gut mucosal cells• Liver cells• RE system cells
RegulationRegulationRegulated by absorption of iron
NOT excretionDietary sourcesAbsorption
◦Must be in ferrous state (Fe++)◦Occurs in the stomach/small intestines
Iron “stores”◦Iron is recycled when RBCs are broken
down ◦25% stored in liver, spleen and bone
marrow as ferritin or (Fe3+)
Iron AbsorptionIron Absorption~10% absorbed in duodenum
and jejunemAbsorption is tightly regulated Absorption controls total body
iron contentOnce absorbed, there is no
mechanism to excrete excess iron
Iron TransportIron TransportAbsorbed iron is
transported in the blood bound to transferrin
Approximately 1% of total body iron is bound to transferrin
Transferrin releases iron to bone marrow to use in hemoglobin
Putting it all together….Putting it all together….
Functions of IronFunctions of IronEssential element of heme,
myoglobin, and hemoglobin
Component of some enzymes involved in cellular oxidative mechanisms
FerritinFerritinSoluble moleculeProtein shell
surrounding an iron core
Can convert iron inside the core into ferric iron for distribution to body cells
Provides a reserve or iron for formation of hemoglobin etc.
HemosiderinHemosiderinAnother storage form of ironPartially deproteinized ferritinInsolubleFound in cells of liver, spleen,
and bone marrowSlowly releases iron
Transport ProteinsTransport Proteins
Apotransferrin◦ Protein in the plasma that moves
iron from one organ to another
Transferrin◦ Glycoprotein formed in the liver◦ Picks up free, ferric form iron from
GI tract and delivers it to specific receptor sites
PorphyrinsPorphyrinsGeneral
structure◦ Cyclic compounds
called tetrapyrroles
◦ Linked by four pyrrole rings bonded by methene bridges
◦ Able to bind metals due to nitrogen atoms
PorphyrinsPorphyrinsColor
◦Purple◦Absorb electromagnetic radiation at
400 nmFluorescence
◦Produce an orange-red fluorescence around the 500-650 nm range
Porphyrin Synthesis & Porphyrin Synthesis & ControlControl Synthesis
◦ Bone marrow and liver are the main site ◦ Synthesis occurs in mitochrondria and cytoplasm
of cell
Control◦ Enzyme: δ-aminolevulinic acid (ALA)
Found in liver◦ Negative Feedback Mechanism◦ Rate of heme syntheis is flexible and can change
rapidly in response to external stimuli
Porphyrins: Ones to keep an Porphyrins: Ones to keep an Eye onEye on Uroporphyrin: URO
◦ Water soluble◦ Heme precursor◦ Found in urine
Coproporphyrin: COPRO◦ Water soluble◦ Heme precursor◦ Found in urine and feces
Protoporphyrin: PROTO◦ Water insoluble◦ Heme precursor◦ Found in feces
PorphyrinogensPorphyrinogensReduced form of porphyrinsFunctional precursor of hemeDifficult to measure due to
instability and colorlessness
Steps to Heme SynthesisSteps to Heme Synthesis
MyoglobinMyoglobinHeme protein found in skeletal and
cardiac muscleMain function is to transport oxygen
from the muscle cell membrane to the mitochondria
Serves as an extra reserve of oxygen to help exercising muscle maintain activity longer
Used to diagnose acute myocardial infarction
LeadLeadFound in the environment and in paintConsidered a toxin
◦ Interferes with hem synthesisExposure primarily respiratory or
gastrointestinal
Half-life in whole blood= 2-3 weeks◦ Half-life= the time required by the body,
tissue or organ to metabolize or inactivate half the amount of substance taken in
LeadLead Absorption
◦ Depends on age, nutritional status and other substances that are present
Transport◦ Once in the blood, 94% transferred to RBC bound to
hgb◦ Once it reaches its half-life, lead is distributed to
soft tissues, such as kidneys, liver and brain. Final storage is in soft tissue(5%) and bone (95%)
Excretion◦ Urine (76%)◦ Feces (16%)◦ Other (8%)
ReferencesReferenceshttp://www.123rf.com/photo_5547046_the-bi
g-truck-transport-iron-ore-in-career.htmlhttp://www.cdc.gov/ncbddd/
hemochromatosis/training/pathophysiology/iron_cycle_popup.htm
Bishop, M., Fody, E., & Schoeff, l. (2010). Clinical Chemistry: Techniques, principles, Correlations. Baltimore: Wolters Kluwer Lippincott Williams & Wilkins.
Sunheimer, R., & Graves, L. (2010). Clinical Laboratory Chemistry. Upper Saddle River: Pearson .