Quantitative analysis of the effect of myristoylated RGT peptide on platelet stable adhesion and spreading on immobilized fibrinogen. (A) Platelets were added to microtiter wells precoated with fibrinogen and allowed to adhere for 60 minutes at 37°C. The phosphatase activity in supernatants (open columns) or in adherent platelets (closed columns) was quantified by a PNPP assay. Data of 3 experiments (mean ± SD) were presented as the ratio of the phosphatase activity of platelet samples over blank. Peptide concentrations: *62.5 μM; **125 μM; ***250 μM. (Inset) The phosphatase activity of myr-RGT-treated platelets adherent to immobilized fibrinogen after removal of the peptide from the buffer. (B) Microphotographs of platelets adherent on fibrinogen and treated with DMSO (B1), myristic acid and RGT peptide at a concentration of 250 μM (B2), scrambled myr-GRT at 250 μM (B3), myr-RGT at 62.5 μM (B4), 125 μM (B5), and 250 μM (B6). DIC indicates differential interference contrast microscopy; IF: immunofluorescence assay with anti-integrin β3 antibody. (C) Platelets were incubated in suspension with different treatments as indicated for 30 minutes at 37°C. The phosphatase activity in supernatants (□) or in remaining platelet suspensions () was quantified by a PNPP assay. Data are arranged as in panel A.