PP1 or wortmannin, but not Y-27632, inhibits platelet spreading on surfaces coated with collagen or anti–integrin β1 antibody.
Washed platelets were incubated without (control [C]) or with 20 μM PP1 (P), 20 μM Y-27632 (Y), and 100 nM wortmannin (W) for 10 minutes at 37°C. Then, they were seeded on surfaces coated with 50 μg/mL collagen (A) or 10 μg/mL anti–integrin β1 (TS2/16) (B) for 30 minutes at 30°C. After unbound platelets were removed, the platelets were fixed, then incubated with TRITC-conjugated phalloidin for actin fiber staining. (C) The extent of platelet spreading was tentatively evaluated as described in the legend for Figure 2. After evaluating more than 200 platelets, the total points for 100 platelets were used as the platelet spreading index. The data represent the mean ± SD of the total points.
