Time course of platelet adhesion to human type I collagen at 1,500/s. Time course of platelet attachment to surface-bound solubilized human type I collagen. The area (square microns) covered by platelets is depicted on the ordinate as a function of time after initiation of blood flow, in minutes (abscissa). The results of three paired comparisons are shown (n = 3; mean ± SEM). (○) High-density donors (mean nMFI = 6.5); (•) low-density donors (mean nMFI = 2.1). The levels of expression of α₂β₁ in high-density donors was threefold that in low-density donors. Differences at 1.5, 2.0, and 2.5 minutes are statistically significant (P < 0.01).