QUANTITATIVE-ANALYSIS OF THROMBOPOIETIN RECEPTORS ON HUMAN MEGAKARYOCYTES

Thrombopoietin (TPO), or c-MPL ligand, is the primary regulator of meg akaryocyte and platelet production. TPO receptors expressed on human m egakaryocytes derived from peripheral blood (PB) and cord blood (CB) p rogenitors cultured in the presence of TPO have now been analyzed quan titatively. Like those on human PB platelets, TPO receptors on the cul tured megakaryocytes exhibited a molecular mass of approximately 80 kD a, Various characteristics of PB-and CB-derived megakaryocytes indicat ed that the former were more mature than the latter, Both PB-and CB-de rived megakaryocytes expressed a single class of high-affinity TPO rec eptors, with 1933+/-772 (n=3) and 184+/-48 (n=4) sites per cell, respe ctively. These data indicate that the number of TPO receptors on human megakaryocytes increases with cell maturation, (C) 1998 Federation of European Biochemical Societies.