Effect of oral aspirin on "ecto-ATPase" activity of washed human platelets.

Aspirin is a potent inhibitor of the platelet release reaction and the accompanying second phase of platelet aggregation. The platelet release reaction is an active, energy-dependent process which appears to require ATP. Eight men ingested 0.32 gm of aspirin daily for 7 days. Although the second phase of 1.7 micron ADP-induced platelet aggregation was absent after aspirin ingestion, the "ecto-ATPase" activities of washed human platelet suspensions were not significantly different before and after ingestion of aspirin. This suggests that the effect of aspirin on the second phase of platelet aggregation is not mediated through inhibition of "ecto-ATPase".