The effect of low dose of 12-O-tetradecanoyl-phorbol-13-acetate on collagen platelet interactions.

We and others have reported that phorbol ester doses ranging from 0.25 to 25 micrograms/ml induce human platelets to aggregate and release serotonin. In this paper, we report the effect of low doses of phorbol (0.5 to 50 ng/ml) on subthreshold amounts of collagen induced platelet aggregation. The platelet aggregation induced by the addition of subthreshold amounts of collagen can be enhanced by low doses of phorbol. The combined low doses of phorbol and subthreshold amounts of collagen induced platelet aggregation can be inhibited by the addition of aspirin and imidazole. The increase in platelet aggregation induced by the combined low doses of phorbol and subthreshold amounts of collagen is probably mediated by the collagen fibril formation.