20. Erythropoietin Mechanism Imbalance Reduces O 2 levels in blood Erythropoietin stimulates red bone marrow Enhanced erythropoiesis increases RBC count Normal blood oxygen levels Stimulus: Hypoxia due to decreased RBC count, decreased availability of O 2 to blood, or increased tissue demands for O 2 Imbalance Start Kidney (and liver to a smaller extent) releases erythropoietin Increases O 2 -carrying ability of blood
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23. Iron For formation of hemoglobin, myoglobin and cytochromes, iron is an important factor. In the human body an average amount of iron is about 4 g (hemoglobin - 65%, myoglobin - 4%, cytochromes - 1%, transferrin - 0.1%, ferritin - 30%). Normal Iron requirements: Adults male : 10 mg/kg Adult female: 20mg/kg pregnancy and lactation: 40 mg/kg
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25. Body Iron Distribution and Storage Dietary iron Utilization Utilization Duodenum (average, 1 - 2 mg per day) Muscle (myoglobin) (300 mg) Liver (1,000 mg) Bone marrow (300 mg) Circulating erythrocytes (hemoglobin) (1,800 mg) Reticuloendothelial macrophages (600 mg) Sloughed mucosal cells Desquamation/Menstruation Other blood loss (average, 1 - 2 mg per day) Storage iron Plasma transferrin (3 mg) Iron loss (Ferritin) (TIBC)
Iron absorption in the intestine is controlled by signaling mechanisms The liver removes and stores excess iron Iron is transported in the plasma in a complex with transferrin Iron is utilized by the muscles to generate myoglobin and by the bone marrow to generate hemoglobin for red blood cells Iron released by tissue breakdown is absorbed and recycled by the body Traces (1 to 2 mg) of iron are lost each day by sloughing of mucosal cells, loss of epithelial cells, blood loss, and menstruation Iron can increase through greater intake of dietary iron, increased efficiency of intestinal absorption, and blood transfusion The human body has not evolved a mechanism to clear excess iron Reference Andrews NC. Disorders of iron metabolism. N Engl J Med . 1999;341:1986-1995.
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