title: Inhibitory effects of P2Y12 receptor antagonists on TRAP-induced platelet aggregation, procoagulant activity, microparticle formation and intracellular calcium responses in patients with acute coronary syndromes.
abstract: Thrombin induces platelet aggregation and membrane rearrangements leading to enhanced procoagulant activity and microparticle production, all of which are thought to contribute to thrombus formation in patients with acute coronary syndromes (ACS). Clopidogrel, an adenosine diphosphate (ADP) receptor antagonist acting at the P2Y(12) receptor, has been shown to provide clinical benefit in ACS. We aimed to investigate the effects of clopidogrel ex vivo and another ADP-antagonist, AR-C69931MX in vitro on thrombin receptor activating peptide (TRAP)-induced platelet aggregation, procoagulant activity, microparticle formation and [Ca(2+)]i responses in patients with ACS. Measurements were performed in platelet-rich plasma using aggregometry and flow cytometry (n = 12). Clopidogrel (300 mg loading dose plus 75 mg daily) significantly inhibited TRAP-induced aggregation, procoagulant activity (annexin V binding) and microparticle production (all P < 0.05) but not as extensively as AR-C69931MX (400 nmol/l). [Ca(2+)]i responses induced by a combination of TRAP and ADP designed to mimic the physiological effects of released ADP showed that clopidogrel partially and AR-C69931MX completely removed the ADP component of the [Ca(2+)]i responses (n = 6). The results provide new information on the mechanisms involved in the beneficial effects of P2Y(12) antagonists in patients with ACS.
authors.affiliation: Division of Cardiovascular Medicine, Queens Medical Centre, Nottingham NG7 2UH, UK.
authors.forename: Miles W H
authors.initials: MW
authors.lastname: Behan
authors.forename: Susan C
authors.initials: SC
authors.lastname: Fox
authors.forename: Stan
authors.initials: S
authors.lastname: Heptinstall
authors.forename: Robert F
authors.initials: RF
authors.lastname: Storey
mesh_terms: D000249:Adenosine Monophosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D020013:Calcium Signaling / Q000187:drug effects; D000077144:Clopidogrel; D003327:Coronary Disease / Q000188:drug therapy / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D008297:Male; D008565:Membrane Proteins / Q000037:antagonists & inhibitors*; D010974:Platelet Aggregation / Q000187:drug effects*; D010975:Platelet Aggregation Inhibitors / Q000008:administration & dosage*; D058919:Purinergic P2 Receptor Antagonists; D058925:Receptors, Purinergic P2Y12; D018179:Receptors, Thrombin / Q000378:metabolism*; D013988:Ticlopidine / Q000008:administration & dosage / Q000031:analogs & derivatives*
chemical_list: D008565:Membrane Proteins; C548576:P2RY12 protein, human; D010975:Platelet Aggregation Inhibitors; D058919:Purinergic P2 Receptor Antagonists; D058925:Receptors, Purinergic P2Y12; D018179:Receptors, Thrombin; D000249:Adenosine Monophosphate; C117446:cangrelor; D000077144:Clopidogrel; D013988:Ticlopidine