Inhibition of ADP-induced platelet aggregation by adenosine tetraphosphate

In contrast to previous reports, highly purified adenosine tetraphosphate (AP4) does not induce the aggregation of platelets but inhibits the aggregation and release reaction in platelet-rich plasma promoted by ADP. The inhibitory action of AP4 on the aggregation by ADP is compared with that of AMP and ATP. The data presented suggest a competitive manner of inhibition of the ADP-induced aggregation by AP4.