TPO is a lineage-specific growth factor produced in the liver, kidney and skeletal muscle. It stimulates the proliferation and maturation of megakaryocytes, and promotes increased circulating levels of platelets in vivo. TPO signals through the c-mpl receptor, and acts as an important regulator of circulating platelets. Human and murine TPO exhibit cross-species reactivity. Recombinant Rat TPO is a fully biologically active 174 amino acid polypeptide (18.7 kDa), which contains the erythropoietin-like domain of the full length TPO protein.