caa a22 4500 475823915 CHVBK 20180406123826.0 cr unu---uuuuu 170329e20000101xx s 000 0 eng 10.1023/A:1018679708251 doi (NATIONALLICENCE)springer-10.1023/A:1018679708251 Role of Extracellular Ionized Calcium in the In Vitro Assessment of GPIIb/IIIa Receptor Antagonists [Elektronische Daten] [Sam Rebello, Jinbao Huang, Jessica Faul, Benedict Lucchesi] Several preclinical studies have found a poor correlation between the ex vivo platelet inhibitory potency and the in vivo antithrombotic efficacy of GPIIb/IIIa receptor antagonists. The present study was designed to examine the differential in vitro potencies of c7E3, MK-383, DMP-728, and SM-20302 in inhibiting ex vivo platelet aggregation under normocalcemic and hypocalcemic conditions. Human blood was collected in either trisodium citrate (0.37%) or PPACK (20 µg/mL). Platelet aggregation assays were performed in platelet-rich plasma from citrate-anticoagulated blood (cPRP) and PPACK-anticoagulated blood (pPRP) using ADP (20 µM) and TRAP (10 µM) as agonists in the presence of c7E3, MK-383, DMP-728, or SM-20302. The concentration of ionized calcium in cPRP was 16-19 times lower than that in pPRP. The IC50 of c7E3 for inhibiting ADP-induced platelet aggregation in cPRP (2.76 ± 0.11 µg/mL) was 1.6 times lower than that in pPRP (4.46 ± 0.48 µg/mL; P < 0.05). Similarly, the IC50 for c7E3 for inhibiting TRAP-induced platelet aggregation in cPRP (4.52 ± 0.34 µg/mL) was 1.7 times lower than that in pPRP (7.69 ± 0.43 µg/mL; P < 0.05). MK-383, DMP-728, and SM-20302 also demonstrated 1.96-, 1.15-, and 1.43-fold lower IC50 values, respectively, in cPRP as compared with pPRP. Chelation of ionized calcium in pPRP led to a progressive increase in platelet inhibition by all the antagonists. These results suggest that the observed in vitro inhibitory potency of a GPIIb/IIIa receptor antagonist is markedly enhanced when trisodium citrate is used as an anticoagulant to collect blood for ex vivo assay. These findings indicate that dosing regimens for GPIIb/IIIa receptor antagonists based on the platelet inhibition profile in citrate may provide misleading information with respect to their true in vivo antithrombotic efficacy. Kluwer Academic Publishers, 2000 GPIIb/IIIa nationallicence trisodium citrate nationallicence PPACK (Phe-Pro-Arg chloromethyl ketone) nationallicence Platelet aggregation nationallicence Rebello Sam Department of Pharmacology, University of Michigan Medical School, Ann Arbor, Michigan, USA aut Huang Jinbao Department of Pharmacology, University of Michigan Medical School, Ann Arbor, Michigan, USA aut Faul Jessica Department of Pharmacology, University of Michigan Medical School, Ann Arbor, Michigan, USA aut Lucchesi Benedict Department of Pharmacology, University of Michigan Medical School, Ann Arbor, Michigan, USA aut Journal of Thrombosis and Thrombolysis Kluwer Academic Publishers 9/1(2000-01-01), 23-28 0929-5305 9:1<23 2000 9 11239 https://doi.org/10.1023/A:1018679708251 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1023/A:1018679708251 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Rebello Sam Department of Pharmacology, University of Michigan Medical School, Ann Arbor, Michigan, USA aut NATIONALLICENCE 700 1- Huang Jinbao Department of Pharmacology, University of Michigan Medical School, Ann Arbor, Michigan, USA aut NATIONALLICENCE 700 1- Faul Jessica Department of Pharmacology, University of Michigan Medical School, Ann Arbor, Michigan, USA aut NATIONALLICENCE 700 1- Lucchesi Benedict Department of Pharmacology, University of Michigan Medical School, Ann Arbor, Michigan, USA aut NATIONALLICENCE 773 0- Journal of Thrombosis and Thrombolysis Kluwer Academic Publishers 9/1(2000-01-01), 23-28 0929-5305 9:1<23 2000 9 11239 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer