AJP - Heart and Circulatory Physiology, Vol 253, Issue 5 1208-H1214, Copyright © 1987 by American Physiological Society
Platelet-collagen adhesion enhances platelet aggregation induced by binding of VWF to platelets
F. M. Laduca, W. R. Bell and R. E. Bettigole
Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205.
Ristocetin-induced platelet aggregation (RIPA) was evaluated in the
presence of platelet-collagen adhesion. RIPA of normal donor platelet-rich
plasma (PRP) demonstrated a primary wave of aggregation mediated by the
binding of von Willebrand factor (VWF) to platelets and a secondary
aggregation wave, due to a platelet-release reaction, initiated by
VWF-platelet binding and inhibitable by acetylsalicylic acid (ASA). An
enhanced RIPA was observed in PRP samples to which collagen had been
previously added. These subthreshold concentrations of collagen, which by
themselves were insufficient to induce aggregation, caused measurable
platelet-collagen adhesion. Subthreshold collagen did not cause
microplatelet aggregation, platelet release of [3H]serotonin, or alter the
dose-responsive binding of 125I-labeled VWF to platelets, which occurred
with increasing ristocetin concentrations. However, ASA inhibition of the
platelet release reaction prevented collagen-enhanced RIPA. These results
demonstrate that platelet-collagen adhesion altered the platelet-release
reaction induced by the binding of VWF to platelets causing a
platelet-release reaction at a level of VWF-platelet binding not normally
initiating a secondary aggregation. These findings suggest that
platelet-collagen adhesion enhances platelet function mediated by VWF.
