Immunocytochemical study on the association between alpha-granule membrane proteins and adhesive proteins during platelet activation.

我们采用了双重染色的方法，免疫细胞化学研究的作用，α-颗粒膜GPIIb/IIIa复合物在凝血酶活化的人血小板表面上的颗粒内纤维蛋白原（Fbg）的表达。在静息血小板中，GPIIb/IIIa均匀分布在α颗粒膜以及包括开放小管系统（OCS）在内的表面膜上，而Fbg仅在颗粒中检测到。在非搅拌条件下用0.1U/ml凝血酶活化后30秒，Fbg与颗粒膜GPIIb/IIIa结合重新分布。在1至5分钟时，与GPIIb/IIIa结合的Fbg在表面膜上的表达增加。尽管如此，在肿胀的OCS的管腔中仍然存在丰富的Fbg，其膜已经耗尽GPIIb/IIIa。与Fbg不同，α-颗粒中大部分丰富的白蛋白被释放到周围介质中，而不与α-颗粒的膜或表面结合。这些结果表明，一小部分的颗粒内Fbg结合到表达在α颗粒膜上的活化的GPIIb/IIIa上的Fbg受体，导致GPIIb/IIIa-Fbg复合物的形成，其然后移动通过OCS膜并在表面膜上表达。因此，α-颗粒膜GPIIb/IIIa充当颗粒内Fbg的载体。

We employed a double-staining method to immunocytochemically study the role of the alpha-granule membrane GPIIb/IIIa complex in the expression of intragranular fibrinogen (Fbg) onto the surface of thrombin-activated human platelets. In the resting platelets, GPIIb/IIIa was distributed evenly on the alpha-granule membrane as well as on the surface membrane including the open canalicular system (OCS), while Fbg was exclusively detected in the granule. At 30 sec after activation by 0.1 U/ml of thrombin under the non-stirring condition, Fbg was redistributed in association with the granule membrane GPIIb/IIIa. At 1 to 5 minutes, the Fbg associating with GPIIb/IIIa became increasingly expressed on the surface membrane. Nevertheless, abundant Fbg was still remaining in the lumen of the swollen OCS, the membrane of which had been already depleted of GPIIb/IIIa. Unlike Fbg, most of the abundant albumin in the alpha-granule was released into the surrounding medium without association to the membrane of either the alpha-granule or the surface. These results suggest that a small portion of the intragranular Fbg binds to Fbg receptors expressed on the activated GPIIb/IIIa on the alpha-granule membrane, resulting in the formation of the GPIIb/IIIa-Fbg complex, which is then moved through the OCS membrane and expressed on the surface membrane. Thus, alpha-granule membrane GPIIb/IIIa acts as a carrier of intragranular Fbg.