Platelet adhesion to collagen in healthy volunteers is influenced by variation of both alpha(2)beta(1) density and von Willebrand factor

Platelet thrombus formation on collagen is initiated by platelet GPIb inter action with von Willebrand factor (vWF) bound to collagen, followed by firm attachment of the platelet to collagen by the integrin alpha(2)beta(1). Pl atelet and plasma vWF levels and alpha(2)beta(1) density on the platelet su rface are highly variable among normal subjects; however, little is known a bout the consequences of this variability on platelet adhesion to collagen. A population of 32 normal subjects was studied to evaluate the relation be tween genetic and phenotypic variations of alpha(2)beta(1) density on the p latelet surface, plasma vWF levels, platelet vWF levels, and adenosine diph osphate and adenosine triphosphate concentrations on the one hand and plate let 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 v WF (r(2) = 0.45 and 0.42, respectively) and alpha(2)beta(1) density on the platelet surface (r(2) = 0.35 and 0.17, not significant). Platelet adhesion to collagen type IV under flow was significantly correlated with platelet vWF levels (r(2) = 0.34) and alpha(2)beta(1) density on the platelet surfac e (r(2) = 0.42). Platelet adhesion to collagen types I and III depends on b oth plasma levels of vWF and alpha(2)beta(1) density on the platelet surfac e, whereas platelet adhesion to collagen type IV is mediated by both platel et VWF levels and alpha(2)beta(1) density on the platelet surface. (Blood. 2000;96:1433-1437) (C) 2000 by The American Society of Hematology.