Rebello S S, Huang J, Faul J D, Lucchesi B R
Department of Pharmacology, University of Michigan Medical School, Ann Arbor, Michigan 48109-0632, USA.
J Thromb Thrombolysis. 2000 Jan;9(1):23-8. doi: 10.1023/a:1018679708251.
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 microg/mL). Platelet aggregation assays were performed in platelet-rich plasma from citrate-anticoagulated blood (cPRP) and PPACK-anticoagulated blood (pPRP) using ADP (20 microM) and TRAP (10 microM) 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 IC(50) of c7E3 for inhibiting ADP-induced platelet aggregation in cPRP (2.76 +/- 0.11 microg/mL) was 1.6 times lower than that in pPRP (4.46 +/- 0.48 microg/mL; P < 0.05). Similarly, the IC(50) for c7E3 for inhibiting TRAP-induced platelet aggregation in cPRP (4.52 +/- 0.34 microg/mL) was 1.7 times lower than that in pPRP (7.69 +/- 0.43 microg/mL; P < 0.05). MK-383, DMP-728, and SM-20302 also demonstrated 1.96-, 1.15-, and 1.43-fold lower IC(50) 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.
多项临床前研究发现，体外血小板抑制效力与体内抗血栓疗效之间的相关性较差。本研究旨在检测c7E3、MK-383、DMP-728和SM-20302在正常血钙和低血钙条件下抑制体外血小板聚集的不同体外效力。血液采集于柠檬酸钠（0.37%）或PPACK（20微克/毫升）中。使用ADP（20微摩尔）和TRAP（10微摩尔）作为激动剂，在c7E3、MK-383、DMP-728或SM-20302存在的情况下，对柠檬酸盐抗凝血液（cPRP）和PPACK抗凝血液（pPRP）中的富血小板血浆进行血小板聚集试验。cPRP中离子钙的浓度比pPRP中低16至19倍。c7E3在cPRP中抑制ADP诱导的血小板聚集的IC50（2.76±0.11微克/毫升）比在pPRP中低1.6倍（4.46±0.48微克/毫升；P<0.05）。同样，c7E3在cPRP中抑制TRAP诱导的血小板聚集的IC50（4.52±0.34微克/毫升）比在pPRP中低1.7倍（7.69±0.43微克/毫升；P<0.05）。与pPRP相比，MK-383、DMP-728和SM-20302在cPRP中的IC50值也分别低1.96倍、1.15倍和1.43倍。pPRP中离子钙的螯合导致所有拮抗剂对血小板的抑制作用逐渐增强。这些结果表明，当使用柠檬酸钠作为抗凝剂采集血液用于体外检测时，观察到的GPIIb/IIIa受体拮抗剂的体外抑制效力显著增强。这些发现表明，基于柠檬酸盐中血小板抑制情况制定的GPIIb/IIIa受体拮抗剂给药方案可能会在其真正的体内抗血栓疗效方面提供误导性信息。
