Effect of apyrase and indomethacin on the aggregation of wild-type platelets.

After pre-incubation with apyrase (in phosphate-buffered saline) or indomethacin (in dimethyl sulfoxide), wild-type platelets were activated with medium or high concentrations of γ-thrombin. Apyrase and indomethacin individually (A) and together (not shown) converted irreversible aggregation induced by a medium concentration of γ-thrombin to reversible aggregation. However, pre-incubation with apyrase, indomethacin, or both (B) did not prevent irreversible aggregation in response to a high concentration of γ-thrombin. Platelets were pre-incubated with the buffer in which apyrase and indomethacin were dissolved as a control.