Inhibition of ADP-induced aggregation of human platelets by beta, gamma-methylene-ATP.

Like ATP the analogue beta, gamma-methylene-ATP (AMP-PCP) is shown to be an inhibitor of both ADP-induced shape change and aggregation of human platelets. The effect of AMP-PCP on aggregation is not dependent on its conversion to adenosine, though in the presence of plasma adenosine is produced and the inhibitory effect is enhanced. Since AMP-PCP cannot be enzymatically cleaved at the beta, gamma-position the inhibitory effect cannot be attributed to utilisation of the analogue by a surface-located ATPase as has been suggested for ATP. Alternative explanations for the effect are considered with respect to some current theories of ADP-induced platelet aggregation.