The effect of arachidonic acid on the aggregability of human platelet rich plasma

Addition of arachidonic acid to human platelet rich plasma caused a reversible aggregation, which was greatly decreased after aspirin ingestion. ADP induced a greater aggregation, which was only slightly decreased after aspirin ingestion. When PRP was incubated with arachidonic acid for 2 or 6 min before the addition of ADP, the ADP-induced aggregation was greatly decreased. This decrease was not changed by aspirin ingestion. The present study indicates that arachidonic acid is metabolized in human platelets not only to aggregatory compounds but also to anti-aggregatory compound(s). The formation of the latter compound is not inhibited by aspirin.