Platelet Density-Dependent Partition of Platelet- von Willebrand Factor Between Alpha Granule and Non-Alpha Granule Pools

Summary In this study, we demonstrate that platelets contain a small hut significant amount of platelet-von Willebrand factor(vWf) not associated with α-granules. When platelets free of plasma proteins are exposed to micromolar concentrations ofdigitonin, plasma membrane permeabilization occurs without disruption of platelet granules. Employing this technique, wehave found that upon exposure of a total platelet population to 8 μM digitonin, 5% of total platelet-vWf is released into the supernatant; this occurs without release of (β-TG from α-granules. When platelets of discrete buoyant density profiles are tested, this extragranular platelet-vWf increased with decreasing platelet density. These findings suggest that a redistribution of platelet-vWf from α-granule to non-granule sites occurs coincident with a decrease inplatelet buoyant density.

[1]  H. Gralnick,et al.  Identification of platelet glycoprotein IIb/IIIa as the major binding site for released platelet-von Willebrand factor. , 1986, Blood.

[2]  H. Gralnick,et al.  Platelet von Willebrand Factor : An Important Determinant of the Bleeding Time in Type I von Willebrand ’ s Disease , 2005 .

[3]  H. Gralnick,et al.  Effect of calcium on the availability of platelet von Willebrand factor. , 1985, Journal of Laboratory and Clinical Medicine.

[4]  M. Ginsberg,et al.  Ultrastructural localization of human platelet thrombospondin, fibrinogen, fibronectin, and von Willebrand factor in frozen thin section. , 1985, Blood.

[5]  H. Gralnick,et al.  A method to minimize platelet activation during platelet isolation. , 1984, Thrombosis research.

[6]  D. Murphy,et al.  Heterogeneity of human whole blood platelet subpopulations. III. Density-dependent differences in subcellular constituents. , 1984, Blood.

[7]  M. Shuman,et al.  Redistribution of alpha-granules and their contents in thrombin- stimulated platelets , 1984, The Journal of cell biology.

[8]  Y. Sultan,et al.  Immunocytochemical localization of factor VIII/von Willebrand factor antigen in human platelets , 1983, Biology of the cell.

[9]  L. Hoyer,et al.  Factor VIII-related protein circulates in normal human plasma as high molecular weight multimers , 1980 .

[10]  J. Akkerman,et al.  Rapid Separation of Cytosol and Particle Fraction of Human Platelets by Digitonin‐induced Cell Damage , 1980, British journal of haematology.

[11]  H. Gralnick,et al.  Heterogeneity of human whole blood platelet subpopulations. I. Relationship between buoyant density, cell volume, and ultrastructure. , 1977, Blood.

[12]  R. Hardisty,et al.  Factor-VIII-related antigen in platelets. , 1974, Thrombosis research.

[13]  P. Zuurendonk,et al.  Rapid separation of particulate components and soluble cytoplasm of isolated rat-liver cells. , 1974, Biochimica et biophysica acta.

[14]  L. Hoyer Immunologic studies of antihemophilic factor (AHF, factor VIII). IV. Radioimmunoassay of AHF antigen. , 1972, The Journal of laboratory and clinical medicine.