Yamaguchi A, Tanoue K, Yamazaki H
Department of Cardiovascular Research, Tokyo Metropolitan Institute of Medical Science, Japan.
Biochim Biophys Acta. 1990 Aug 13;1054(1):8-13. doi: 10.1016/0167-4889(90)90198-m.
We have previously found that stimulation of aequorin-loaded platelets by thrombin produced a two-peaked increase in intracellular free calcium concentration ([Ca2+]i), and the development of the second peak of [Ca2+]i was closely related with the aggregation. In this report, we studied the interrelationship between the GPIIb/IIIa complex, aggregation, cytoskeletons and [Ca2+]i of platelets. The pretreatment of the platelets with dihydrocytochalasin B (4 microM), an actin polymerization inhibitor, did not inhibit aggregation and TXB2 production, but did inhibit both actin polymerization and the second peak of [Ca2+]i increase induced by thrombin, suggesting that actin polymerization and the second peak of [Ca2+]i are interrelated. GRGDSP (100 microM), a synthetic anti-adhesive peptide, has already been reported to inhibit platelet aggregation and the second peak of [Ca2+]i induced by thrombin. It also inhibited actin polymerization and TXB2 production, suggesting that aggregation was important for not only the generation of the second peak of [Ca2+]i but also for actin polymerization and TXB2 production. PGI2 (5 nM) did not abolish but only delayed aggregation, TXB2 production, actin polymerization and the second peak of [Ca2+]i increase. These findings suggest that the secondary signals are caused by aggregation (fibrinogen-binding to the GPIIb/IIIa) in thrombin-aggregated platelets, which results in the TXA2 production and the secondary peak of [Ca2+]i increase, and the latter was dependent on actin polymerization.
我们先前发现，凝血酶刺激装载水母发光蛋白的血小板会使细胞内游离钙浓度（[Ca2+]i）出现双峰增加，且[Ca2+]i第二个峰的出现与聚集密切相关。在本报告中，我们研究了血小板的糖蛋白IIb/IIIa复合物、聚集、细胞骨架和[Ca2+]i之间的相互关系。用肌动蛋白聚合抑制剂二氢细胞松弛素B（4 microM）预处理血小板，并不抑制聚集和TXB2的产生，但确实抑制了肌动蛋白聚合以及凝血酶诱导的[Ca2+]i增加的第二个峰，这表明肌动蛋白聚合和[Ca2+]i的第二个峰是相互关联的。GRGDSP（100 microM）是一种合成抗黏附肽，已有报道称其可抑制血小板聚集以及凝血酶诱导的[Ca2+]i第二个峰。它还抑制肌动蛋白聚合和TXB2的产生，这表明聚集不仅对[Ca2+]i第二个峰的产生很重要，而且对肌动蛋白聚合和TXB2的产生也很重要。前列环素（PGI2，5 nM）并没有消除而是仅延迟了聚集、TXB2的产生、肌动蛋白聚合以及[Ca2+]i增加的第二个峰。这些发现表明，在凝血酶诱导聚集的血小板中，次级信号是由聚集（纤维蛋白原与糖蛋白IIb/IIIa结合）引起的，这导致了血栓素A2的产生以及[Ca2+]i增加的第二个峰，而后者依赖于肌动蛋白聚合。
