Efficiency and specificity of the plasminogen cross-talk. Glu-plasminogen (2μM) was bound to platelets as indicated in “Activation of platelet-bound plasminogen by monocytes or neurons.” (A) After treatment with 50 μg/mL CpB, adherent monocytes were incubated with 5 × 10⁶ platelets bearing plasminogen (cross-talk) or with plasminogen (concentration equivalent to plasminogen bound to platelets; same surface) in the presence of 0.75mM CBS0065. In a parallel experiment, uPA (concentration equivalent to uPA bound to monocytes) was incubated with 5 × 10⁶ platelets bearing plasminogen (free uPA) in the presence of 0.75mM CBS0065. Results are expressed as the rate of plasmin formation (mean ± SEM; n = 3; triplicates). NS indicates nonsignificant (P = .078), *P < .005, #P < .014. (B) Monocytes were incubated with 1nM of native uPA and various concentrations of a nonactive mutant uPA (r-scuPA-Gly¹⁵⁹). Monocytes were then incubated with 5 × 10⁶ platelets bearing plasminogen, in the presence of 0.75mM CBS0065. The formation of plasmin (mOD/minute) was detected by measuring the release of p-nitroaniline (mean ± SEM; n = 2; triplicates). A representative experiment is shown (P = .023; 0 vs 5nM r-scuPA-Gly¹⁵⁹).