Yamaguchi A, Yamamoto N, Kitagawa H, Tanoue K, Yamazaki H
Department of Cardiovascular Research, Tokyo Metropolitan Institute of Medical Science, Japan.
FEBS Lett. 1987 Dec 10;225(1-2):228-32. doi: 10.1016/0014-5793(87)81163-8.
When aequorin-loaded platelets were stimulated with thrombin, the luminescence signal of aequorin showed two peaks. From experiments with 1 mM external Ca2+ or EGTA, both one-half of the first peak and the entire second peak reflected the influx of Ca2+ from the external medium, and the remaining half of the first peak reflected the mobilization of Ca2+ from its storage site. A monoclonal antibody (TM83) that recognizes the glycoprotein IIb/IIIa (GPIIb/IIIa) complex which has binding sites for fibrinogen and the synthetic peptide GRGDSP are known to inhibit fibrinogen binding and platelet aggregation. Both eliminated the second peak of intracellular free calcium ([Ca2+]i). Similar effects were observed during activation by collagen, but not during PMA activation. It was concluded that the GPIIb/IIIa complex was intimately related to a part of the Ca2+ influx during the activation of platelets.
当用凝血酶刺激装载了水母发光蛋白的血小板时，水母发光蛋白的发光信号出现两个峰值。通过在1 mM的细胞外Ca2+或乙二醇双四乙酸（EGTA）存在的情况下进行实验发现，第一个峰值的一半以及整个第二个峰值反映了Ca2+从细胞外介质的流入，而第一个峰值的另一半则反映了Ca2+从其储存位点的动员。一种识别糖蛋白IIb/IIIa（GPIIb/IIIa）复合物（该复合物具有与纤维蛋白原结合的位点）的单克隆抗体（TM83）以及合成肽GRGDSP，已知它们可抑制纤维蛋白原结合和血小板聚集。二者均消除了细胞内游离钙（[Ca2+]i）的第二个峰值。在由胶原蛋白激活过程中观察到了类似的效应，但在佛波酯（PMA）激活过程中未观察到。得出的结论是，GPIIb/IIIa复合物与血小板激活过程中一部分Ca2+的流入密切相关。
