Fibrinogen synthesis by megakaryocyte rich human marrow cell concentrates

A rapid method is described for the production of a human marrow cell suspension highly enriched in megakaryocytes. These concentrates were incubated with radiolabelled amino-acids, and cell lysates were then analysed for fibrinogen synthesis. Neosynthesized proteins were detected by immunoprecipitation, immuno-affinity chromatography and electrophoresis. Fluorography of the electrophoresis gels showed three radioactive bands corresponding to the three chains of cold fibrinogen. Immunoblotting and autoradiography of bidimensional, nonreduced-reduced electrophoresis gels showed that these three proteins were joined by disulfide bonds in the cell. These results suggest that megakaryocytes synthesize fibrinogen, and imply that platelet fibrinogen is of megakaryocytic origin.