The A4 peptide inhibits ristocetin- and shear-induced platelet aggregation. (A) A4 peptide inhibits ristocetin-induced aggregation of PRP. (B) Shows that 1.6 μM A4 peptide plus 32 μM Pep-1 or 6.4 μM A4 peptide plus 128 μM Pep-1 inhibits shear-induced aggregation of washed platelets after 2 minutes. The use of 6.4 μM scrambled A4 peptide plus 128 μM Pep-1 (S-A4) does not inhibit shear-induced platelet aggregation (in the far left panel of A, the amount of Pep-1 added was 128 μM; representative of 2 separate experiments).