Both TXA 2 generation and ADP secretion are required as amplifiers of PMP shedding. Except for high-dose collagen, eptifibatide abolished agonist-induced PMPs release. The TP receptor antagonist SQ-29,548 and the P2Y 12 receptor antagonist PSB-0739 markedly inhibited PMPs induced by low doses of collagen.

The ADP scavenger apyrase reduced PMPs induced by U46619 (1256, 395–2908 vs. 2840, 2404–3031 PMPs/μL n = 3, P < 0.01) but did not affect the response to epinephrine or ADP. ASA reduced PMPs induced by AA- (645, 347–2946 vs.

ADP-triggered PMPs shedding was dose-independent. The strongest response was to high concentration collagen. Platelet agonists induced annexin V-positive PMPs shedding. PMPs were detected by flow-cytometry using CD61 and annexin-V as fluorescent markers. Platelet-rich plasma from healthy subjects was stimulated with arachidonic acid (AA), U46619, collagen type-I (10 and 1.5 μg/mL), epinephrine, ADP or TRAP-6 and pre-incubated with acetylsalicylic acid (ASA, 100 and 10 μmol/L), SQ-29,548, apyrase, PSB-0739, or eptifibatide. The present study investigated the cellular events regulating PMPs shedding, testing in vitro platelet agonists and inhibitors.

Platelet microparticles (PMPs) contribute to thrombogenesis but the effects of antiplatelet drugs on PMPs generation is undefined.

1.0 coblyn