Transitory failure of ADP to induce platelet aggregation in plasma from a young healthy woman

Platelet rich plasma was prepared from venous blood sampled from a healthy young female. ADP(2.5 - 250 microgram) failed to induce platelet aggregation when added to the plasma shortly after the collection of blood, but later addition of ADP induced normal aggregation. Serial dilution of the female's platelet-rich plasma with plasma of normal aggregability was followed by a progresively increasing aggregation amplitude. It is suggested that the impaired aggregation observed shortly after blood sampling was due to a transitory high concentration of prostacyclin in the female's plasma.