Figure 2.

αIIb-mediated outside-in signaling requires fibrinogen binding and aggregation. (A) Aggregation traces of VGTΔ724 platelets treated with D3 (30 μg/mL) in the presence of Fg (250 μg/mL), with or without the peptide RGDS (1 mM) or the mAb 7E3 (10 μg/mL) (RGDS and 7E3 prevent Fg binding to αIIbβ3). (B) D3 plus Fg-induced TxA₂ production and ATP secretion by VGTΔ724 platelets treated with substances that inhibit Fg binding to αIIbβ3. (C) Aggregation traces of (450 μL) normal and VGTΔ724 platelets in response to D3 (30 μg/mL) plus Fg (250 μg/mL) without stirring. (D) TxA₂ production by normal and VGTΔ724 platelets was measured at zero time and every 2 minutes for 8 minutes; the final concentration of secreted ATP also was measured. Data shown here were from 3 experiments. The error bars represent SD, n = 3. In some cases, the values of the SD were so small that the bars cannot be seen.