As with the DW, RGDW only partially inhibits clot retraction; αIIbβ3 activation is required for retraction of preformed fibrin. (A) Washed platelets (3 × 10⁸/mL) were treated with the RGDW (150 µM) for 20 minutes at room temperature and then transferred to an aggregometer cuvette containing 0.2 U/mL Thr and 2 mM CaCl₂ to initiate clot retraction. The area of the clot is shown underneath each photograph and expressed in square pixels. (B) SEM images of clot retraction after 15 minutes. (C) Washed platelets were untreated (sample 1) or stimulated to undergo clot retraction with the following: Thr + CaCl₂ (sample 2), or soluble fibrin + CaCl₂ alone (sample 3), or in combination with 15 μg/mL of the mAb PT25-2 (sample 4), or 25 μM T6 (sample 5). Photographs of the time course of clot retraction are shown. The area of the clot is shown underneath each photograph and expressed in square pixels. Data shown in panels A and C are representative of at least 3 independent experiments.