SHEAR STRESS-INDUCED DETACHMENT OF BLOOD-PLATELETS FROM VARIOUS SURFACES

Platelet accumulation is the result of platelet adhesion and detachmen t. 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 sh ear stress. Platelets adhering to fibronectin and laminin were most ea sily detached. Fibrinogen and VWF had an intermediate position. Almost no detachment occurred from ECM and collagen type III. Dendritic plat elets were removed more easily than spread platelets. When the shear r ate at which adhesion had occurred was raised, platelet detachment dec reased 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 settl e, then by the nature of the surface, and then by the degree of spread ing. The shear optimum for a given adhesive protein is not determined by the detachment.