Description_x000D_ Biochem/physiol Actions_x000D_ Erythropoietin, a glycoprotein produced primarily by the kidneys and at lower levels by the liver, is the primary regulatory factor of erythropoiesis. EPO promotes the proliferation, differentiation, and survival of the erythroid progenitors. EPO stimulates erythropoiesis by inducing growth and differentiation of burst forming units and colony forming units into mature red blood cells. EPO produced by kidney cells is increased in response to hypoxia or anemia._x000D_ The biological effects of erythropoietin are mediated by the erythropoietin receptor, which binds EPO with high affinity and is a potent EPO antagonist. When EPO is present at low concentrations, the EPO receptor initiates prolongation of G1 in the cell cycle and sends a differentiation signal; whereas at high EPO concentrations, a proliferation signal is generated and the G1 is shortened._x000D_ Erythropoietin is a glycoprotein that is the principal regulator of red blood cell growth and differentiation._x000D_ Physical form_x000D_ Lyophilized from a 0.2 μm filtered solution in phosphate buffered saline containing 0.5 mg bovine serum albumin._x000D_ Preparation Note_x000D_ This Erythropoietin (EPO) is produced from a DNA sequence encoding rat erythropoietin (Met 1-Arg 192). Mature soluble recombinant rat EPO has Ala 27 at the amino terminus. The 166 amino acid residue soluble EPO has a calculated molecular mass of approximately 18.5 kDa. Due to glycosylation, the recombinant protein migrates as a 22-26 kDa in SDS-PAGE. Erythropoietin has been cloned from various species including human, murine, canine, etc. The mature proteins from the various species are highly conserved, exhibiting greater than 80% amino acid sequence identity. Rat EPO cDNA encodes a 192 amino acid residue precursor protein that is processed to yield a 166 amino acid residue mature protein. EPO contains 3 N-linked glycosylation sites. Glycosylation of EPO is required for the biological activities of EPO in vivo._x000D_ Analysis Note_x000D_ The biological acitivity is measured by its ability to stimulate cell proliferation using TF-1 cell line.