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.
Keywords
Platelet-vWf - Platelet density - Alpha granules
