- Platelet activation uses a complex set of pathways to respond to vascular injury during hemostasis. However, thrombosis relies on the same set of pathways. Antiplatelet therapies used to prevent thrombotic events often target the P2Y₁₂ platelet receptor for inhibition but can result in bleeding diathesis or in abnormally high ADP levels in the blood. Thus, an ATP secretion assay was used to measure dense granule release in order to elucidate pathways involved in platelet activation and degranulation. P2Y₁₂ inhibition with PAR1 activation resulted in enhanced dense granule release, but PAR4 and GPVI activation did not have any effect. PLCβ and PKC δ inhibition and calcium
chelation reduced dense granule release, while PI3K, PAR1, P2Y₁, and GP IIb/IIIa inhibition did not have an impact. It is possible that there is an ADP-mediated response mechanism that releases dense granules in a secondary wave if P2Y₁₂ is inhibited, which should be further examined.