Inhibition of platelet aggregation by granulocytes stimulated during experimental trauma

The effect of granulocytes, stimulated in vivo by standardized soft tissue trauma, on the aggregation of autologous platelets in vitro, was studied in the pig. Platelet aggregation induced by ADP and arachidonic acid was inhibited when platelets harvested before trauma were incubated with granulocytes obtained 5 min after trauma. The granulocytes were separated from the platelets during the incubation by enclosure in dialysis tubes. Platelet inhibition was evident when the cell cohorts were suspended in cell-free medium as well as in autologous plasma extracted before trauma. In addition, incubation of platelets harvested before trauma with plasma obtained after trauma decreased platelet aggregation. In conclusion, granulocytes stimulated in vivo inhibited platelet function in vitro. Platelet inhibitory activity was shown to be related with the granulocytes per se, but also with factors present in plasma after trauma.