Comparative kinetic curves of platelet-driven clot contraction in whole blood (black) vs PRP (red) in the absence (control) and presence of the following platelet inhibitors. 1 μM PGE₁ (A), 200 μM blebbistatin (B), 100 μg/mL abciximab (C), 4 μM latrunculin A (D), 10 μM atopaxar (E), and 25 μM tirofiban (F). Note that the inhibitory effects on clot contraction in whole blood are only partial, whereas in PRP the inhibition is complete. The citrated blood or plasma samples were preincubated with the inhibitors at 37°C for 3 minutes before the initiation of clotting and clot contraction by thrombin (1 U/mL). The averaged curves from 4 or 5 experiments with blood samples from independent donors are presented as the mean ± standard error of the mean.