Iron, Porphyrin, and Hemoglobin Flashcards
iron metabolism
is the set of chemical reactions maintaining homeostasis of iron. The control of this necessary since excess or deficiency is significant to health and disease states.
State of Iron in Diet
Ferric (Fe3+)
State of Iron Absorbed
Ferretin (Fe2+)
How is Iron Stored?
Ferretin (Fe2+) is oxidized back to Ferric
(Fe3+)2(Fe3+) Ferric bound to apoferritin
How is Iron Transported?
Ferretin (Fe2+) is oxidized back to Ferric (Fe3+)
2(FE3+) Ferric bound to transferrin
Form of Iron bound to Heme
Ferretin (Fe2+)
Role of Ferritin (Fe2+):
molecule for intestinal absorption
incorporation with Heme Molecule
Role of Ferric (Fe3+)
molecule for transportation and storage
Role of Transferrin
binds to 2 ferric molecules for transportation
prevents loss through kidney
Define TIBC
Total Iron Binding Capacity (TIBC):
The theoretical amount of iron that could be bound if transferrin and other minor iron binding proteins present in the serum or plasma sample were fully saturated.
Transferrin Saturation Calculation
= Iron Concentration / TIBC
Low Transferrin Saturation:
Low Iron / High TIBC
High Transferrin Saturation
High Iron / Low TIBC
Reference Range: Iron (Fe)
65 – 175 ug/dl
Reference Range: TIBC
240 – 420 ug/dl
Reference Range: Transferrin
180 – 400 mg/dl
Reference Range: Ferretin (Fe2+)
Male 25 – 300 ng/ml
Female 10 – 130 ng/ml (menstruating)
Female 25 – 300 ng/ml (post-menopause)
%Fe Saturation
25 – 40 %
Decreased Total Iron (causes/symptoms)
↑ Demand (Pregnancy) ↑ Loss (blood loss) ↓ Release of stored Fe (infection impairs release) ↓ Absorption ↓ Dietary Intake (Fe Deficient anemia)
Increased Total Iron (causes/symptoms)
↑ release of Fe (hemolysis)
↓ Utilization of Fe (lead poisoning)
↑ Absorbance (hemochromatosis or hemsosiderosis)
Defective Storage
Increased Ferretin (Fe2+)
Iron Overdose Liver Disease Chronic Renal Failure Malignancy Infection/Inflammation
Decreased ferretin (Fe2+)
Malnutrition
earliest indicator of deficiency
diagnostic of iron deficiency
Increased Transferrin
Iron Deficient anemia ↑Transferrin ↓ Ferretin
Iron Deficiency (inverse to ferritin)
Decreased Transferrin
Chronic Infection
Malnutrition
iron Overdose
Role of Haptoglobin
produced by liver “Heme scavenger”
Transports free hemoglobin that is extracellular to be removed by liver
- Hemolysis causes increase of extracellular hemoglobin
- Haptoglobin binds to free hemoglobin for transportation
- Haptoglobin brings free hemoglobin to liver for processing
Prevents loss of hemoglobin
significance of and situations in which changes in haptoglobin con¬centration occur
Decrease Caused by:
Hemolysis (hemolytic anemia, HDN, transfusion rxn) all haptoglobin bound
Liver Disease (liver not producing Haptoglobin)
Nephrotic syndrome
Haptoglobin Reference Range
Haptoglobin Normal: 35 – 200 mg/dl
Iron (Fe) Measurement
- Create acidic pH
- Releases Iron from transferrin
- Reduce Ferriic (Fe3+) to Ferriton (Fe2+)
- Form color complex to Ferriton (Fe2+)
- Read spectrophotometrically
Iron Measurment Interference
hemolysis
EDTA
citrate
oxalate
TIBC Measurement
- 500ug excess Ferric iron added (Fe3+) pH 7.5
- All available transferrin sites are bound
- Supernatant analyzed for Ferric Iron (Fe3+) TIBC
- TIBC = TOTAL Fe + UIBC
UIBC: Unbound Iron Binding Capacity
TIBC Calculation
TIBC = TOTAL Fe + UIBC
UIBC: Unbound Iron Binding Capacity
Transferrin Measurement (Indirect)
indirectly measure using TIBC
Transferrin = TIBC X 0.70
Transferrin Measurement (Direct)
TURBIDOMETRIC
Transferrin + Anti-transferrin Antibody forms antigen/antibody complex
Change in the absorbance measured at 340 nm
Porphyrin:
chelate metals to form the functional groups that participate in oxidative metabolism
Not biologically active but a intermediate for hemoglobin and myoglobin synthesis
three clinically significant porphyrins
- Uroporphyrin (urine excretion)
- Coproporphyrin (urine or feces excretion) 3. Protoporphyrin (feces excretion)
Porphyrin Indicates abnormal heme synthesis when in excess
effect of U.V. light on porphyrins
Porphyrins absorb visible light causing itchy skin, fluid accumulation, blisters, swelling
Extremely photosensitive causing severe reaction upon exposure to sunlight (UV)
List and describe the components of heme and heme synthesis
1 .The first step in heme synthesis takes place in the mitochondrion, with the condensation of succinyl CoA and glycine by ALA synthase to form 5-aminolevulic acid (ALA).
- ALA is transported to the cytosol where a series of reactions produce a ring structure called coproporphyrinogen III.
- Coproporphyrinogen III returns to the mitochondrion where an addition reaction produces protoporhyrin IX.
- The enzyme ferrochelatase inserts iron into the ring structure of protoporphyrin IX to produce heme
Makeup of Heme
Porphyrin + Iron
significance of ALA synthetase in the regulation of heme synthesis
ALA synthase is an enzyme that catalyzes condensation of glycine and Succinyl CO A
MAIN REGULATOR of porphyrin synthesis (precursor to heme
Rapid response to negative feedback
↓ HEME = ↑ ALA Synthase Production
factors which affect the activity of ALA syn¬thetase
Hereditary Defect/deficiency (enzyme)
x-linked sideroblastic anemia microcytic,hypochromic (small and low heme)
Fe overload
Siderblasts found in the bone marrow
ALA Synthase requires coenzyme (coenzyme doesn’t work/ALA doesn’t work) Impaired Heme synthesis
Porphyria
accumulation of porphyrins and their precursors
healthy individual has trace amounts of porphyrins since all porphyrins get converted to heme
PORPHYRIA CLASSIFICATION
ORGAN INVOLVEMENT:
Erythropoietic Porphyria
- accumulation of excess porphyrins in blood producing tissues (bone marrow)
Hepatic Porphyria
- accumulation of excess porphyrins in liver
PORPHYRIA CLASSIFICATION
ACQUISITION:
Inherited:
-genetic defect causing excess cells
Acquireed:
-liver disease, toxic metals, drugs causing excess in urine
PORPHYRIA CLASSIFICATION
SYMPTOMS:
Cutaneous:
-skin manifestations, photosensitivity
Neurologic:
-abdominal pain, psychological disorders
Differentiate porphyrinuria vs. porphyria.
Porphyria: excess porphyrins or its precursors (indicates disruption in heme synthesis)
Porphyrinurea: secondary porphyria
Mild to moderate increase in the excretion of urinary porphyrins is seen
Caused by of non-inherited defect in heme synthesis but rather drug or toxin interference
Cutaneous Symptoms:
-skin manifestations, photosensitivity, skin lesions, discolored teeth, solar eczema, Itchy skin, fluid accumulation, blisters, swelling, disfiguring
Excess porphyrin production and excretion:
Uroporphyrin
Coproporphyrin
Protoporphyrin
Cutaneous Porphyrias
PCT: Porphyria Cutanea Tardia (hepatic #1)
EP: Erythropoietic Porphyria
CEP: Congenital Erythropoietic Porphyria
Neurologic Porphyria Symptoms:
-abdominal pain (constipation vomiting), psychological disorders (confusion, anxiety, depression, schizophrenia)
Excess of early precursors – ALA and PBG
Types of Neurologic Porphyrias:
AIP: Acute Intermittant Porphyria (hepatic #2)
VP: Variegate Porphyria
HCP: Hereditary Coproporphyria
Drugs and Chemicals Causing Porphyrias:
Drugs Chemicals Sedatives Alcohol Anticonvulsants Lead Steroid Hormones Insecticides Sulfonamides
Samples for porphyria testing
Random Urine (fresh morning collection)
24 Hour Urine (sodium bicarbonate preservative)
1 gram Feces
(store frozen & protected from light)
Screening Method for Porphyria
Watson-Schwartz Test
Sample for Watson-Schwartz test
First Morning Spot Urine
Reagent for Watson-Schwartz
Erhlich’s Reagent
Interference for Watson-Scwartz
urobilinogen, indole
Confirmation for Watson-Scwartz
Extract with chloroform or butanal
Hoesch Test
No Interference
Quantitative Test for Porphyrias
PBG isolated using ion-exchange column (removes urobilinogen)
Eluted, condensed, Erlich’s reagent added
Measured via spectrophotometry
Sample: 24 hour Urine
mechanisms by which lead poisoning inter¬feres in heme synthesis
lead inhibits enzymes in the porphyrin pathway resulting in increases of substrates, which are subsequently eliminated and can be measured in urine. Cannot complete pathway to synthesize heme.
- Delta-ALA-Dehydrase
- Coproporphyrinogen Oxide
- Ferrochelatase
Order of bands for Electrophorisis of hemoglobin on Cellulose citrate.
A F S C
Cellulose Acetate
Alkaline pH, Moves way from application point to anode
Citrate Gel
Acid ph, Moves in both directions away from application to anode and cathode (more separation of bands)
Define Hemoglobinopathy
Defect in structure of hemoglobin
Symptoms of Hemoglobinopathy
Asymptomatic Initially nfections Aseptic necrosis of bone Retinopathy (clots in eye) Renal Concentrating Defects Cerebral Thombosis Delayed Growth and Sexual maturation
Define Thalassemia.
Normal structure of hemoglobin but a defect in quantity of hemoglobin
Decreased synthesis of globin gains alpha or beta
Lab Results: ↓ ferretin (Fe2), %SAT,
↑ transferrin, TIBC
Differentiate myoglobin from hemoglobin
Hemogobin:
Heme protein carried on RBCs
Structure: 3% heme and 97% globulin gains (alpha, beta, gamma, delta)
4 hemes + 4 globulins
Function: transport oxygen to tissues and CO2 back to lungs
Buffering system
Myoglobin:
Heme protein in skeletal and cardiac muslces
Structure: 1 heme + 1 globin (1/4th the size of Hgb)
Function: transport oxygen to muscle cells
conditions in which you would see increased myoglobin.
Heart Attack (MI) releases myoglobin Skeletal Muscle Injury releases myoglobin
(cannot differentiate between skeletal and cardiac myoglobin)
