Erythropoietin
Erythropoietin (EPO) is a hormone found in the human body. It is secreted from the peritubular cells in the kidneys. EPO is composed of a 165 amino acid chain with four oligosaccharide side chains. It is classified as a peptide hormone.
Secretion and Production
Production of EPO is stimulated by low oxygen levels in the blood. After secretion, EPO binds to receptors on the surface of red cell precursors, stimulating them to transform into mature red blood cells. This causes a rise in the amount of oxygen that reaches the kidneys, and consequently a reduction in production of EPO.
The primary effect of EPO is to regulate red blood cell production. EPO increases the oxygen-carrying capacity of the blood, therefore increasing the aerobic respiratory capacity of the muscles.
Pharmacological Uses
EPO was first isolated from human urine in 1977, and its structure was first identified in 1983. The first form of synthetic EPO was produced by mammalian-cell technology in 1989. EPO can be administered subcutaneously or intravenously. There are several uses of EPO as a drug:
Anemia
EPO is commonly used for both cancer and renal disease patients who suffer from anemia. Anemia is a frequent side effect of chemotherapy, and synthetic EPO can help to raise the number of red blood cells produced, therefore combating anemia. The same is true for renal failure. Because EPO is secreted from the kidneys, renal failure can inhibit this secretion. Synthetic EPO is generally administered to patients on dialysis to combat anemia.
Blood Transfusion
EPO is commonly administered to patients who are either scheduled to receive a blood transfusion or scheduled to undergo surgery. If blood loss is expected in either of these cases, EPO may be administered in order to increase the patient’s concentration of red blood cells, therefore preventing anemia if significant blood loss does occur.
Blood Doping
Though it is illegal for athletes to use EPO as a performance-enhancement drug, many choose to do so anyway. EPO increases the aerobic respiratory capacity of the muscles, therefore making it a viable drug to athletes, especially those who participate in marathons or multi-stage bicycle races. The danger of using EPO as a blood-doping drug is that excessive use can thicken the blood so much that it can strain the heart. In the early 1990s, many athletes died from heart failure in their sleep due to overuse of EPO.