钙离子螯合对糖蛋白IIb/IIIa拮抗剂阿昔单抗、依替巴肽和替罗非班血小板抑制能力的影响。

Effect of Ca2+ chelation on the platelet inhibitory ability of the GPIIb/IIIa antagonists abciximab, eptifibatide and tirofiban.

作者信息

Marciniak S J, Jordan R E, Mascelli M A

机构信息

Centocor, Malvern, PA 19355, USA.

出版信息

Thromb Haemost. 2001 Mar;85(3):539-43.

PMID:11307828

Abstract

OBJECTIVE

Enhanced GPIIb/IIIa binding and inhibition of platelet aggregation of eptifibatide by the reduction of ionized plasma calcium concentrations have been reported. The present study compared the importance of Ca2+ chelation on the in vitro platelet inhibitory profiles of the GPIIb/IIIa antagonists abciximab, eptifibatide and tirofiban.

METHODS AND RESULTS

Turbidimetric platelet aggregation dose response curves of the various GPIIb/IIIa antagonists were performed using platelet rich plasma (PRP) anticoagulated with either trisodium citrate, or the non-chelating anticoagulant, PPACK. The concentrations of antagonist that resulted in 50% inhibition of TRAP-induced (10 microM) platelet aggregation (IC50) were measured in the presence of either citrate or PPACK. In addition, the influence of Ca2+ chelation on the binding properties (relative affinity, on- and off-rates) of abciximab for the GPIIb/IIIa receptor on platelets was measured. For all three agonists, the IC50 concentrations were lower for platelets treated with citrate than PPACK, but the degree of difference varied among the agents. The mean TRAP IC50 values for citrate and PPACK were 88.2 +/- 12.2 nM and 126.1 +/- 28.4 nM for abciximab (1.4 fold enhancement; p = 0.0007), 75.9 +/- 13.3 nM and 142.6 +/- 32.6 nM for tirofiban (1.9-fold enhancement; p = 0.001), and 260.2 +/- 62.5 nM and 810.3 +/- 182.5 nM for eptifibatide (3.1-fold enhancement; p = 0.001). A similar shift in effective inhibitor concentrations for abciximab was observed with ADP (10 microM). The relative affinities (EC50), on- and off-rates of abciximab for the platelet GPIIb/IIIa receptor in the presence of trisodium citrate and PPACK were equivalent.

CONCLUSIONS

These data confirm previous observations that Ca2+ chelation afforded by citrate decreases the effective inhibitor concentrations of GPIIb/IIIa antagonists, as assessed by turbidimetric platelet aggregation. However, the extent of decrease was less for abciximab and tirofiban, compared to eptifibatide.

摘要

目的

有报道称，离子化血浆钙浓度降低可增强依替巴肽与 GPIIb/IIIa 的结合并抑制血小板聚集。本研究比较了 Ca2+螯合对 GPIIb/IIIa 拮抗剂阿昔单抗、依替巴肽和替罗非班体外血小板抑制谱的重要性。

方法与结果

使用用柠檬酸钠或非螯合抗凝剂 PPACK 抗凝的富血小板血浆（PRP）绘制各种 GPIIb/IIIa 拮抗剂的比浊法血小板聚集剂量反应曲线。在存在柠檬酸盐或 PPACK 的情况下，测量导致 TRAP 诱导（10 microM）的血小板聚集抑制 50%（IC50）的拮抗剂浓度。此外，还测量了 Ca2+螯合对阿昔单抗与血小板上 GPIIb/IIIa 受体结合特性（相对亲和力、结合和解离速率）的影响。对于所有三种激动剂，用柠檬酸盐处理的血小板的 IC50 浓度低于用 PPACK 处理的血小板，但不同药物之间的差异程度有所不同。阿昔单抗在柠檬酸盐和 PPACK 存在下的平均 TRAP IC50 值分别为 88.2±12.2 nM 和 126.1±28.4 nM（增强 1.4 倍；p = 0.0007），替罗非班为 75.9±13.3 nM 和 142.6±32.6 nM（增强 1.9 倍；p = 0.001），依替巴肽为 260.2±62.5 nM 和 810.3±182.5 nM（增强 3.1 倍；p = 0.001）。用 ADP（10 microM）观察到阿昔单抗有效抑制剂浓度有类似的变化。在存在柠檬酸钠和 PPACK 的情况下，阿昔单抗对血小板 GPIIb/IIIa 受体的相对亲和力（EC50）、结合和解离速率相当。