The influence of salicylate on platelets and whole blood adenine nucleotides.

1. The addition of sodium salicylate to freshly withdrawn human blood or native platelet-rich plasma significantly delays platelet aggregation in vitro.2. The administration of acetylsalicylic acid to human subjects also significantly delays platelet aggregation in their whole blood and there is a short delay in the formation of fibrin but this is not statistically significant.3. Salicylate, whether added to human blood in vitro as sodium salicylate or given by mouth as acetylsalicylic acid, significantly reduces the platelet clumping activity of adenosine diphosphate (ADP) added to whole blood in vitro.4. The administration of aspirin in high doses for several days produces a marked increase in the total adenine nucleotide content of whole blood. The percentage of adenosine triphosphate (ATP) was increased, that of ADP decreased while there is an obvious increase in the ATP: ADP ratio.5. There is little correlation between the plasma salicylate level and the delay aspirin produces in platelet aggregation in vitro or the changes that occur in the levels of ADP or ATP in whole blood during administration of aspirin.6. Significant correlations do occur, however, between the delay in platelet aggregation in vitro and (i) the percentage increase in the ATP concentration, (ii) the percentage decrease in ADP concentration, (iii) the percentage change in the ATP: ADP ratio observed during aspirin administration.