Platelet-mediated clot retraction. PRP samples prepared from wild-type (+/+), α_IIb^+/−, and α_Iib^−/− mice were clotted by the addition of thrombin, and the progress of clot retraction was followed for 15 hours at 37°C.

(A) t = 0 hours. (B) t = 2 hours. (C) t = 15 hours. The platelet-rich plasma (PRP) was obtained by centrifugation at 70g, and plasma was obtained by further centrifugation at 2500g in a F2402 rotor (Beckman). PRP at a concentration of 1 × 10⁵ platelets/μL in 270-μL was incubated at 37°C in the presence of 30 μL CaCl₂ (50 mmol/L). Clot formation was performed with 1 U prewarmed human thrombin (Sigma). PRP from wild-type animals had completed the retraction of the opaque clots in a 2-hour period, whereas the clot retraction for the α_IIb^+/− mice was incomplete. PRP of α_IIb^−/− failed to induce clot retraction for 15 hours.