Chapter

Erythropoietins, Erythropoietic Factors, and Erythropoiesis

Part of the series Milestones in Drug Therapy pp 3-18

Erythropoiesis: an overview

  • Bruce E. TorbettAffiliated withDepartment of Molecular and Experimental Medicine, The Scripps Research Institute
  • , Jeffrey S. FriedmanAffiliated withDepartment of Molecular and Experimental Medicine, The Scripps Research Institute

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Abstract

Red blood cell production in vertebrates is dynamic and tightly regulated with losses due to senescence or bleeding in normal individuals being balanced by generation of new red cells. The main function of the red cells is to transport oxygen from the lungs to tissues in all parts of the body and to transport carbon dioxide back for exchange. Healthy adult humans maintain a total of 2–3×1013 erythrocytes at any given time, with men having 5–6 million and woman having 4–5 million erythrocytes/microliter blood [1]. The normal life span of an erythrocyte is approximately 120 days in the blood requiring a daily replacement of about 1% of the circulating erythrocytes [1]. To put the numbers of red cells needed daily into perspective, in an adult human maintenance of steady-state red cell numbers requires the generation of 2×106 erythrocytes every second. Moreover, basal oxygen consumption is 4 mL/kg/min and body stores are approximately five times greater, emphasizing the need to maintain a stable red cell mass while having the capacity to increase red cells during times of tissue hypoxia [1,2]. Changes in the production of erythrocytes from a steady-level will occur in response to blood loss, increased oxygen demand, altered erythrocyte lifespan, or diseases.