Platelet adhesion to collagen in healthy volunteers is influenced by variation of both a2ß1 density and von Willebrand factor

Platelet thrombus formation on collagen is initiated by platelet GPIb interaction with von Willebrand factor (vWF) bound to collagen, followed by firm attachment of the platelet to collagen by the integrin a2ß1. Platelet and plasma vWF levels and a2ß1 density on the platelet surface are highly variable among normal subjects; however, little is known about the consequences of this variability on platelet adhesion to collagen. A population of 32 normal subjects was studied to evaluate the relation between genetic and phenotypic variations of a2ß1 density on the platelet surface, plasma vWF levels, platelet vWF levels, and adenosine diphosphate and adenosine triphosphate concentrations on the one hand and platelet adhesion to collagen under flow on the other hand. Platelet adhesion to collagen types I and III under flow was correlated with plasma levels of vWF (r2?=?0.45 and 0.42, respectively) and a2ß1 density on the platelet surface (r2?=?0.35 and 0.17, not significant). Platelet adhesion to collagen type IV under flow was significantly correlated with platelet vWF levels (r2?=?0.34) and a2ß1 density on the platelet surface (r2?=?0.42). Platelet adhesion to collagen types I and III depends on both plasma levels of vWF and a2ß1 density on the platelet surface, whereas platelet adhesion to collagen type IV is mediated by both platelet vWF levels and a2ß1 density on the platelet surface.