Effect of the calpain inhibitors ALLM and ALLN on the contraction of thrombin-induced fibrin clots in PRP. PRP was preincubated with 500 μM of ALLM, 500 μM of ALLN, or an equal volume of dimethyl sulfoxide solvent control for 40 minutes before 1 U/mL of thrombin to induce fibrin clot formation. The kinetics of clot formation and contraction were then imaged in real time in a Thromboimager as described in Figure 1. The upper plots show averaged kinetic curves (mean ± standard deviation; n = 8) in the absence and presence of ALLM (A) or ALLN (B), along with the first derivatives shown as dashed (control) and solid blue lines (inhibitors). Phase 1 is on the left and phase 2 is on the right of the corresponding dotted vertical borderlines. The lower plots represent pairwise comparisons of the parameters of clot contraction in the absence and presence of the calpain inhibitors. a.u., arbitrary unit.