A 4-year-old African boy is brought in by his adoptive
parents who say that he has pain in his limbs and
does not want to walk
What affects the normal functions of an erythrocyte?
Eric Niederhoffer
SIU-SOM
Red Blood Cell: Biochemistry
and Sickle Cell Disease
• RBC structure
size, spectrin, channels
• Metabolism
glycolysis (2,3-BPG), pentose phosphate pathway (G6PDH, NADPH), glutathione
• Hemoglobin
genes, heme, Mb/Hb (normal), HbS (defect), fibers (sickling and inflammation),
thalassemia
An Erythrocyte (RBC)
Reference Ranges
RBCs, male 4.3-5.9 x 106/µL
female
3.5-5.5 x 106/µL
Hb, male
13.5-17.5 g/dL
female
12.0-16.0 g/dL
Hct, male
41-53%
female
36-46%
MCV
80-100 fL
MCH
25.4-34.6 pg
MCHC
31-36 %
RDW
11-14.5 %
Practical Values
65% of Fe in Hb
1 g Hb = 3.46 mg Fe
1 mL blood at 15 g/dL Hb = 0.5 mg Fe
RBC x 3 = Hb
Hb x 3 = Hct
Microcytic < 80 fL
Macrocytic > 100 fL
Erythrocyte Membrane Composition
http://www.ruf.rice.edu/~bioslabs/studies/sds-page/rbcmembrane.html
RBC Metabolic Pathways
GSH
Glc
G6P
NADP+ + H+
PGI
GSSG
GR
F6P
PFK
NADPH
F16BP
aldolase
DHAP
G3P
G3PDH
BPG mutase
1,3-BPG
PGK
2,3-BPG
3PG
G6PDH
lactonase
6PGDH
CO2
6PG
PPP
PGM
2,3-BPG phosphatase
2PG
enolase
PEP
Lactate
No O2
LDH
H2O
GP
HK
Glycolysis
H2O2
PK
Pyr
3-7 C metabolites
(R5P, F6P, G3P)
Hemoglobin Genes and Gene Products
http://www.mun.ca/biology/desmid/brian/BIOL3530/DB_Ch09/fig9_24.jpg
Hemoglobin Gene Product Production
Yolk sac
Liver
HbF: 2α and 2γ
HbE: 2ζ and 2ε
Spleen
Bone marrow
HbA1: 2α and 2β
HbA2: 2α and 2δ
Mehta, A. B., and A. V. Hoffbrand. 2000. Haematology at a glance, Blackwell Science, Malden, Mass.
Myoglobin and Hemoglobin Structure
Glu6→Val6
oxyMb (MbO2)
deoxyMb
oxyHb (HbO2)

deoxyHb
O2

O2
O2
O2

O2

Glu6→Val6
Hemoglobin Structure Changes
http://www.mfi.ku.dk/PPaulev/chapter8/images/8-3.jpg
Sickle Cell Disease
(>6 major genotypes)
at least 1 sickle gene, hemoglobin S (HbS) ≥ 50% Hb present.
homozygotic HbSS (sickle cell anemia) - HbS = 100% Hb present
HbS beta-0 thalassemia - Severe double heterozygote for HbS and beta-0 thalassemia;
almost indistinguishable from sickle cell anemia phenotypically (MCV low)
HbSC disease - Double heterozygote for HbS and HbC, with intermediate clinical severity
HbS/hereditary persistence of fetal hemoglobin (S/HPHP) - Mild form or symptom free
HbS/HbE syndrome - Rare and generally mild clinical course
Rare combinations of HbS with HbD Los Angeles, HbO Arab, G-Philadelphia, among others
http://www.emedicine.com/ped/TOPIC2096.HTM
Hemoglobin Electrophoresis
Anode (+)
Homozygous
HbS
Heterozygous
HbS
Relative
protein
charge
Normal
adult
Normal
neonate
HbSC
Cathode (-)
Start (samples applied here)
http://themedicalbiochemistrypage.org/hemoglobin-myoglobin.html
Molecular Changes of HbS
Heme
Val
http://www.sicklecellinfo.net/fiberformation.htm.
Daniel J. Harrington, D. J., K. Adachi, and W. E. Royer, Jr. 1997. J. Mol. Biol. 272(3):398-407
Molecular and Cellular Changes of HbS
Decreased PO2
Permanent damage to RBC
Cell⟺endothelium interactions
http://www.emedicine.com/ped/TOPIC2096.HTM
Effects of Therapy with Hydroxyurea
★
★
★
http://www.emedicine.com/ped/TOPIC2096.HTM
Thalassemias
α-thalassemia
Hb Barts (γ4)
HbH (β4)
β-thalassemia
Review Questions
• What proteins compose the membrane of erythrocytes?
• What metabolic pathways are used in erythrocytes?
• What is hemoglobin; what changes with sickle cell
disease?
• What clinical observations would you make concerning
patients with SCD?
• What are the thalassemias?