Suzuki H, Kaneko T, Sakamoto T, Nakagawa M, Miyamoto T, Yamada M, Tanoue K
Department of Cardiovascular Research, Tokyo Metropolitan Institute of Medical Science, Japan.
J Electron Microsc (Tokyo). 1994 Oct;43(5):282-9.
Treatment of human washed platelets with 5 mM EDTA at 37 degrees for 60 min irreversibly dissociated glycoprotein (GP) IIb/IIIa complex (alpha IIb beta 3 integrin) on the surface membrane, since transmission immunoelectron microscopy studies demonstrated that these EDTA-pretreated platelets in the presence of added Ca2+ ion could not bind P2, an anti-GPIIb/IIIa complex-specific monoclonal antibody, to their surface membrane. The treatment, however, had no effect on the GPIIb/IIIa complex on the alpha-granule membrane. At 30 sec after the EDTA-pretreated platelets were activated with 0.1 U/ml of thrombin, alpha-granules fused with each other or with the surface-connected canalicular system (SCCS) to form swollen SCCS, the membrane of which was found to have the intact GPIIb/IIIa complex detectable by P2. In addition, at this time the intact GPIIb/IIIa complex reappeared on the surface membrane. At 5 min, the intact GPIIb/IIIa complex increased on the surface membrane with a reciprocal decrease or disappearance on the membrane of the swollen SCCS. The observation under scanning immunoelectron microscopy also confirmed the same translocation of the intact GPIIb/IIIa complex. These results indicate that alpha-granule membrane GPIIb/IIIa is redistributed to the surface membrane via the membrane of SCCS during the release reaction.
在37℃用5 mM乙二胺四乙酸（EDTA）处理人洗涤血小板60分钟，可使表面膜上的糖蛋白（GP）IIb/IIIa复合物（αIIbβ3整合素）不可逆地解离，因为透射免疫电子显微镜研究表明，这些经EDTA预处理的血小板在添加Ca2+离子的情况下，不能使其表面膜结合抗GPIIb/IIIa复合物特异性单克隆抗体P2。然而，该处理对α颗粒膜上的GPIIb/IIIa复合物没有影响。在用0.1 U/ml凝血酶激活经EDTA预处理的血小板后30秒，α颗粒相互融合或与表面连接的小管系统（SCCS）融合形成肿胀的SCCS，发现其膜上有可被P2检测到的完整GPIIb/IIIa复合物。此外，此时完整的GPIIb/IIIa复合物重新出现在表面膜上。在5分钟时，完整的GPIIb/IIIa复合物在表面膜上增加，而在肿胀的SCCS膜上则相应减少或消失。扫描免疫电子显微镜观察也证实了完整的GPIIb/IIIa复合物有相同的转位。这些结果表明，在释放反应过程中，α颗粒膜GPIIb/IIIa通过SCCS膜重新分布到表面膜上。
