Inhibition of platelet aggregation by ADP preincubated on HUVECs.

HUVEC-containing wells and blank wells were incubated with a phosphate-free buffer containing 1-75 μmol/L ADP at 37°C for 15 minutes. (A) When 50 μmol/L ADP was incubated on HUVECs, it lost most of its agonistic activity for platelets. The arrows indicate addition of the incubation buffer from HUVECs or blank wells. The results are representative of 3 experiments. (B) Pi was liberated from ADP preincubated on HUVECs in a dose-dependent manner relative to the concentration of ADP added (▩). Almost no Pi was liberated from ADP preincubated on blank wells (open columns). The ADP-containing buffer preincubated on HUVECs (●) lost its agonistic activity for platelets in comparison with the ADP-containing buffer preincubated on blank wells (○). The ADP-treated incubation buffer was added to PRP in a 10-fold dilution. The results are the mean ± SD of 3 separate experiments.