Shear-stress-induced detachment of blood platelets from various surfaces.

Platelet accumulation is the result of platelet adhesion and detachment. This study describes platelet detachment from fibronectin, laminin, fibrinogen, von Willebrand Factor (vWF), endothelial cell matrix (ECM), and collagen type III. Platelets adhered after 5 minutes' perfusion of anticoagulated whole blood at different shear rates were subjected to a brief flush of 1 minute with HEPES-buffered saline at varying shear stress. Platelets adhering to fibronectin and laminin were most easily detached. Fibrinogen and vWF had an intermediate position. Almost no detachment occurred from ECM and collagen type III. Dendritic platelets were removed more easily than spread platelets. When the shear rate at which adhesion had occurred was raised, platelet detachment decreased strongly. When the time period between adhesion and detachment was increased, platelet detachment also decreased. From these results, we conclude that detachment is determined initially by the shear rate at which platelets adhere, then by the time they are allowed to settle, then by the nature of the surface, and then by the degree of spreading. The shear optimum for a given adhesive protein is not determined by the detachment.