Highly efficient induction of human platelet aggregation in heparinized platelet-rich plasma by diadenosine triphosphate (Ap3A).

Diadenosine triphosphate (Ap3A), which is a releasable dinucleotide of human platelets, induces platelet aggregation when added to heparinized platelet-rich plasma. The concentration dependence of the dinucleotide is similar to ADP. This finding is fully compatible with our recent report of the low potency of Ap3A in citrated platelet-rich plasma relative to ADP. The aggregatory effect of Ap3A in heparinized versus citrated plasma is reflected in the corresponding rates of Ap3A degradation. In citrated plasma, the hydrolysis of Ap3A is drastically slowed down because the hydrolase needs divalent metal ions. The results strongly support the assumption that the aggregatory effect of Ap3A is mediated by the enzymatic hydrolysis of Ap3A which generates ADP as the ultimate stimulus.