Erythropoietin (EPO) is a glycoprotein hormone that is principally known for its role in erythropoiesis, where it is responsible for stimulating proliferation and differentiation of erythroid progenitor cells. The differentiation of CFU-E (Colony Forming Unit-Erythroid) cells into erythrocytes can only be accomplished in the presence of EPO. Physiological levels of EPO in adult mammals are maintained primarily by the kidneys, whereas levels in fetal or neonatal mammals are maintained by the liver. EPO also can exert various non-hematopoietic activities, including vascularization and proliferation of smooth muscle, neural protection during hypoxia, and stimulation of certain B cells. PeproTech's Human EPO contains 166 amino acid residues and has a calculated molecular weight of approximately 18.4 kDa. As a result of glycosylation, Recombinant Human EPO migrates with an apparent molecular mass of 37.0 kDa by SDS-PAGE gel, under reducing and non-reducing conditions.