Comparison of thrombin- and SFLLRN-stimulated platelet aggregation in the absence or presence of the calpain inhibitor ALLM. Comparison of the turbidimetric aggregation of washed human platelets stimulated by either thrombin (1 U/mL) or the platelet thrombin receptor activation peptide SFLLRN (50 μM): thrombin (A), thrombin plus ALLM (B), SFLLRN (C), and SFLLRN plus ALLM (D). The effect of ALLM on platelet aggregation was measured after preincubating the washed platelets with 500 μM of ALLM for 15 minutes at 37°C.