Figure 2.

ADP stimulation promotes adhesion and spreading of FcR γ-chain–deficient mouse platelets on collagen. (A, 1) Washed murine platelets (3 × 10⁷/ml) from wild-type mice (+/+) were pretreated with the inhibitor cocktail and seeded on BSA- or collagen-coated coverslips and stained as described in Fig. 1. Photo images are representative of 5–10 different images from three experiments. (A, 2) The graph illustrates the mean number of adhered platelets ± SEM per 0.028 mm² from seven different images from at least two separate experiments. (B, 1) Washed platelets (3 × 10⁷/ml) from FcR γ-chain (+/+) or (−/−) mice were pretreated with 100 μM EGTA, 10 μM indomethacin, and 10 μM lotrafiban, with or without 10 μg/ml anti–mouse integrin α₂ antibody for 10 min. ADP (10 μM) was present in parts i, iii, and iv. The ADP receptor antagonists A3P5P (1 mM) plus AR-C67085 (1 μM) were present in part ii. Platelets were seeded on BSA- or collagen-coated coverslips and stained as described in Fig. 1. (B, 2) The mean number of adhered platelets ± SEM per 0.028 mm² from 10 different images from three experiments is shown. One asterisk denotes P < 0.05, and two asterisks denote P < 0.01. The maximal diameter of between 100 and 200 adhered platelets was measured. For adhered platelets on BSA-coated surfaces, diameters of 10 platelets were counted because of a lack of cells.