Thromb Haemost 1994; 72(06): 947-956
DOI: 10.1055/s-0038-1648989
Original Article
Schattauer GmbH Stuttgart

Thrombin-stimulated Human Platelets Express Molecular Forms of α-Granule Factor V (FV), which Differ from FVa

Authors

  • Edward G Wyshock

    The Sol Sherry Thrombosis Research Center, Temple University School of Medicine, Philadelphia, PA, USA
  • Gwendolyn J Stewart

    The Sol Sherry Thrombosis Research Center, Temple University School of Medicine, Philadelphia, PA, USA
  • Robert W Colman

    The Sol Sherry Thrombosis Research Center, Temple University School of Medicine, Philadelphia, PA, USA
Further Information

Publication History

Received 06 June 1994

Accepted after revision 18 August 1994

Publication Date:
06 July 2018 (online)

Preview

Summary

Binding of 125I-Fab fragments of chain-specific antibodies indicate that both heavy and light chains of a-granule factor Va (FVa) were externalized on the platelet membrane after stimulation with thrombin. Using a Mab against the activation peptide of factor V (FV), the epitope appears on the stimulated platelet surface. Half as much light chain and heavy chain (FVa) was expressed compared to the activation peptide, suggesting that expression of α-granule FV occurs after thrombin stimulation. Using an ELISA, we find that 32% of a-granule FV was released and 68% is retained in the platelet pellet. Immunoblots of platelets indicate that FV exists in 200 kDa und 150 kDa forms, representing incomplete cleavage, while the releasate demonstrates a more complete cleavage by proteases. We conclude that expression of α-granule FV is quantitatively greater than that released and exists in molecular forms which cannot be completely explained by the binding of FVa.