title: Purification and properties of a megakaryocyte stimulatory factor present both in the serum-free conditioned medium of human embryonic kidney cells and in thrombocytopenic plasma.
abstract: Megakaryocyte stimulatory factor (MSF) has been purified to homogeneity (7.5 X 10(5)-fold) from serum-free conditioned medium obtained from cultured human embryonic kidney cells and to near homogeneity (1.44 X 10(7)-fold) from thrombocytopenic rabbit plasma. MSF activity from either source was assayed by its ability to enhance the rate of synthesis of platelet factor 4-like proteins in a rat promegakaryoblast cell line. The 125I-labeled factor prepared from human embryonic kidney cell conditioned medium is homogeneous as judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and isoelectric focusing in the presence of 9.2 M urea. MSF obtained from the above source is an acidic protein (pI = 5.1) with an Mr = 15,000 which stimulates platelet factor 4-like protein synthesis in rat promegakaryoblast cells by as much as 7-fold, and exhibits half-maximal activity at a concentration of 0.8 pM. MSF was also purified from thrombocytopenic rabbit plasma by a nearly identical isolation procedure, and 125I-labeled factor prepared from this source also possessed an Mr = 15,000. MSF exhibited no biologic activity corresponding to other known hemopoietic growth factors, and appears to be specific for the megakaryocyte lineage.
mesh_terms: D000818:Animals; D001681:Biological Assay; D002460:Cell Line; D002845:Chromatography; D003470:Culture Media; D004591:Electrophoresis, Polyacrylamide Gel; D004622:Embryo, Mammalian; D006801:Humans; D007525:Isoelectric Focusing; D007668:Kidney / Q000378:metabolism*; D008533:Megakaryocytes / Q000378:metabolism; D010978:Platelet Factor 4 / Q000096:biosynthesis; D011506:Proteins / Q000302:isolation & purification* / Q000494:pharmacology; D011509:Proteoglycans; D011817:Rabbits; D051381:Rats; D013921:Thrombocytopenia / Q000097:blood*; D000099158:Proteoglycan 4
chemical_list: D003470:Culture Media; D010978:Platelet Factor 4; D011506:Proteins; D011509:Proteoglycans; C419197:PRG4 protein, human; D000099158:Proteoglycan 4