Platelet recovery from aspirin inhibition in vivo; differing patterns under various assay conditions.

The linear return of platelet malondialdhyde (MDA) production after aspirin ingestion as described by Stuart et al.4 has been widely accepted as a nonisotopic method for the determination of platelet survival. However. using assays for platelet prostaglandin production and cyclooxygenase activity. a number of authors2’ ’1 have now reported a 24 to 48-hr delay in recovery after aspirin. This delay has been interpreted as evidence that aspirin inhibits megakaryocyte as well as platelet cyclooxygenase. The discrepancy in these findings has not been explained. We have measured the return of production of MDA and thromboxane B2 (TXB2) by platelets of normal volunteers after a single dose of aspirin using a variety of assay conditions. We find striking differences in the pattern of recovery depending upon the presence of protein in the medium in which the platelets are stimulated. Production of both MDA and TXB2 returns in a linear fashion with time when platelets are washed. resuspended in buffer and stimulated with either NEM or thrombin. A 48-hr lag in recovery is seen when platelets are stimulated in whole