Effects of plasma fibronectin concentration in the perfusate on platelet thrombus formation on collagen under shear conditions. A suspension of platelets and red blood cells was premixed with or without 50, 100, 250, or 500 μg/mL soluble fibronectin (FN) and 5 μM LPA in the absence or presence of 2 μM FUD over surfaces coated with 20 μg/mL collagen at a wall shear rate of 1250 s^–1 for 5 minutes. (A) Microscopy was performed as described in Figure 2. Bar = 100 μm. (B) Thrombus volume and number of adherent platelets were calculated as described in Figure 3. Squares indicate plasma fibronectin alone at various concentrations. The triangles indicate 250 μg/mL plasma fibronectin plus 2 μM FUD. Values represent the mean ± SD (n = 3).