In Vitro Mechanism of Platelet Aggregation (PA) by Purified Plasma Membrane Vesicles (PMV) Shed by Mouse 15091A Tumor Cells

G.J. Gasic, J. L. Catalfamo, T. B. Gasic, N. Avdalovic
1979 VIIth International Congress on Thrombosis and Haemostasis   unpublished
Cell transformation leads to increased blebbing of the plasma membrane and release of PMV with capacity for PA in the presence of heparin or hirudin (G.J. Stewart et al.). This PA is preceded by a lag of 2or more min. To investigate whether vesicle binding is a prerequisite for PA, 125I-lebelled vesicles were added to rat or mouse platelet rich plasma in the aggregometer, and radioactivity was measured in pellet and supernate fractions of samples taken at different time intervals. Most of the
more » ... dioactivity was found with pelleted platelets, this association reached a maximal plateau at the mid point of the lag period. After 125I-label led vesicles interacted with platelets, characteristic polypeptide bands present in autoradiograms of SDS-PAGE of 125I-labelled vesicles alone were also present in SDS solubiliicd pellet fractions. Binding of radioactivity by platelets depended on a plasma cofactor(s) other than fibronogen since gel filtered platelets failed to bind 125I-labelled vesicles when fibronogen was added but did so in the presence of plasma; plasma was also required for aggregation. Isolation of the active fraction by step ammonium sulfate (AS) fractionation of plasma or its adsorption by barium citrate followed by AS elution, suggests that it may be a clotting factor(s) or a unique protein(s) that cofractionates with the prothrombin complex. In addition to its role in binding, this protein(s), when activated by vesicles or the platelet-vesicle complex, might also participate in PA.
doi:10.1055/s-0039-1687370 fatcat:nuf2vjyxubbebnwffl5gvno6ca