Fate of Red Blood Cells

Dr. Wasif Haq

Structure of mature red blood cells• Mature Erythrocyte devoid of Nucleus,

Mitochondria & Endoplasmic reticulum.• Cell membrane elasticity.• Passive in nature.• Utilize anaerobic respiration.• Contain Hemoglobin & enzymes.

Function of enzymes in erythrocytes

• Membrane flexibility.• Ions transportation.• Iron in Ferrous form, not in Ferric form.• Protein oxidation in red blood cells prevented.

Eventual fate of Red blood cells

• Approx life span=100-120 days.• Self destruction (Eryptosis)• Eryptosis vs Apoptosis?• Spleen=Grave yard of red blood cells.• A non-functional or severely damaged red

blood cell may be removed earlier.

Mechanism of Eryptosis

• Triggered by glucose depletion, oxidative stress, osmotic shock, bacterial cell wall components, drugs & certain metal ions.

• Membrane fragility increases=Slowing of metabolism, deficiency of new enzymes & energy.

• Cell membrane blebbing, cell shrinkage & Phosphatidylserine activation, attracting macrophages.

• Rupture during circulation & in pulp of spleen.

Eryptosis- Influencing factors

• Eryptosis rate= Erythropoiesis rate. • Significance?• Role of Erythropoietin?• Increased Eryptosis: Sepsis, malaria, sickle cell

anemia, Iron deficiency, B-Thalessemia, Lead & Mercury intoxication.

• Decreased Eryptosis: Urea, Catecholamines & Nitric Oxide.

Fate of Hemoglobin• Hemoglobin released in circulation.• Phagocytized by macrophages in body, especially

liver, spleen & bone marrow.• Hemolyzed hemoglobin bound with plasma protein

called haptoglobin which prevents its excretion.• Iron released by Macrophages which is carried by

transferrin.• Porphyrin converted to bilirubin. • Iron may be recirculated or transported to liver for

storage in form of Ferritin.

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