Exocytosis of platelet alpha granule contents

Alpha granules contain mainly polypeptides such as fibrinogen, von Willebrand factor, growth factors and protease inhibitors that supplement thrombin generation at the site of injury. In addtion to their role in hemostasis, platelets also contain angiogenesis stimulators and inhibitors (Italiano et al. 2008).α颗粒主要由纤维蛋白原、冯·维勒布兰德因子、生长因子和蛋白酶抑制剂等多肽组成，这些成分在损伤部位补充凝血酶的生成。除了在止血过程中的作用外，血小板还含有血管生成促进剂和抑制剂（Italiano et al. 2008）。