Inhibition of ADP-induced platelet aggregation by AMP degraded on HUVECs.

HUVEC-containing wells and blank wells were incubated with a phosphate-free buffer containing 1-100 μmol/L AMP at 37°C for 15 minutes. (A) We added 50 μmol/L AMP buffer preincubated on HUVECs to PRP in 10-fold dilution just before activation by ADP (final concentration, 3 μmol/L). Platelet aggregation was inhibited compared with the AMP buffer preincubated on blank wells. The arrows indicate the addition of ADP. The result is representative of 3 experiments.(B) Although AMP was not hydrolyzed on blank wells (■), Pi was liberated from AMP on HUVECs in a dose-dependent manner relative to the concentration of AMP added (▩). AMP buffer preincubated on HUVECs inhibited ADP-induced platelet aggregation (●), whereas AMP buffer preincubated on blank wells did not affect aggregation significantly (○). The results are the mean ± SD of 3 separate experiments.