Erythropoietin

Erythropoietin (EPO) is also known as hematopoietic or hemopoietin is a glycoprotein cytokine secrete by the kidney in response to cellular hypoxia; it stimulates red blood cells production (erythropoiesis) in the bone marrow. Low levels of EPO (around 10 mU/mL) are constantly secreted sufficient to compensate for normal red blood cell turn over. Common causes of cellular hypoxia resulting in elevated levels of EPO (upto 10,000 mU/mL) include by anemia and hypoxemia due to chronic lung disease. Erythropoietin is produced by intenstitial fibroblasts in the kidney in close association with peritubular capillary and proximal convoluted tubule. It is also produced in perisinusoidal cells in the liver. EPO is highly glycosylated (40% of total molecular weight ) with half life in blood around five hours.
Erythropoietin is an essential hormone for red blood cells production. Without it definitive erythropoiesis does not take place.
Erythropoietin has been shown its effects by binding to the erythropoietin receptor (EPOR). EPO binds to the erythropoietin receptor on the red cell progenitor surface and activates a JAK 2 signaling cascade. This initiate STAT5, PIK3, and Ras MAPK pathways. This results in differentiation, survival and proliferation of erythroid cell.