Bertolino G, Noris P, Spedini P, Balduini C L
Department of Internal Medicine, University of Pavia-IRCCS S. Matteo, Italy.
Thromb Haemost. 1995 Apr;73(4):689-92.
We found that intracellular Ca2+ concentration ([Ca2+]i) increased during ristocetin-induced agglutination of aequorin loaded platelets resuspended in plasma. Chelation of extracellular Ca2+ had no effect on platelet clumping, but delayed and greatly reduced Ca2+ increase, indicating that it derived for the most part from Ca2+ influx. Nine monoclonal antibodies (MA) against glycoprotein (GP) Ib largely prevented ristocetin-induced platelet clumping and [Ca2+]i increase, while three anti-GPIb MA with no effect on platelet clumping did not interfere with Ca2+ movement. In unstirred samples platelet agglutination was greatly reduced and [Ca2+]i increase was abolished, suggesting that close platelet-to-platelet contact, in addition to von Willebrand factor (vWF) binding to GPIb, is necessary for Ca2+ transient. Nine MA against GPIIb/IIIa, the gly-arg-gly-asp-ser (GRGDS) peptide and GPIIb/IIIa complex dissociation had no effect on platelet agglutination, but significantly reduced Ca2+ increase. Our results suggest that platelet clumping induced by vWF binding to GPIb is responsible for GPIIb-IIIa dependent Ca2+ influx.
我们发现，在将负载水母发光蛋白的血小板重悬于血浆中并经瑞斯托菌素诱导发生凝集的过程中，细胞内钙离子浓度（[Ca2+]i）升高。细胞外钙离子的螯合对血小板聚集没有影响，但延迟并大幅降低了钙离子的升高，这表明其大部分来源于钙离子内流。九种抗糖蛋白（GP）Ib单克隆抗体（MA）在很大程度上阻止了瑞斯托菌素诱导的血小板聚集和[Ca2+]i升高，而三种对血小板聚集无影响的抗GPIb MA并未干扰钙离子移动。在未搅拌的样本中，血小板凝集大幅减少，[Ca2+]i升高被消除，这表明除了血管性血友病因子（vWF）与GPIb结合外，血小板与血小板之间的紧密接触对于钙离子瞬变也是必要的。九种抗GPIIb/IIIa单克隆抗体、甘氨酸-精氨酸-甘氨酸-天冬氨酸-丝氨酸（GRGDS）肽以及GPIIb/IIIa复合物解离对血小板凝集没有影响，但显著降低了钙离子的升高。我们的结果表明，vWF与GPIb结合诱导的血小板聚集是GPIIb-IIIa依赖性钙离子内流的原因。
