White J G, Krumwiede M D
Department of Laboratory Medicine, University of Minnesota Medical School, Minneapolis 55455.
Eur J Cell Biol. 1994 Oct;65(1):178-88.
Events occurring on the exposed luminal surface of blood platelets during interaction with foreign surfaces have been evaluated in detail, but the down-side has received less attention. The present study has examined the interaction of platelets with glass precoated with fibrinogen-gold (Fgn/Au), latex spherules, or cationized ferritin (CF) and compared their organization on the ventral surface with the fate of the same particulates when added to platelets already spread on glass or formvar grids. Platelets spread readily on the particle-coated glass surface. During early stages of interaction, particles of Fgn/Au, CF and latex were taken up by channels of the open canalicular system (OCS). Fgn/Au and CF often reached the dorsal surface through OCS channels where they were moved to platelet centers. In contrast, layers of Fgn/Au, CF and latex remained evenly dispersed from edge to edge on the down-side of spread platelets. Clearance of particulates from peripheral and intermediate to central zones under spread platelets was not observed. Particulates did not move from the up-side around platelet margins to the down-side, or from the ventral surface around edges to the up-side, unless spread cells were in contact. Thus, particulates use the OCS as a two-way street. The persistence of evenly dispersed layers of Fgn/Au, CF or latex on precoated glass under spread or spreading platelets indicates a significant difference in the way particulates are handled on the free upside and bound down-side. The results support the concept that the main purpose of mobile receptors is to facilitate spreading, and that the down-side is a protected zone of adhesion.
血小板与异物表面相互作用时，其暴露的管腔表面所发生的事件已得到详细评估，但血小板的底面却较少受到关注。本研究检测了血小板与预先包被有纤维蛋白原-金（Fgn/Au）、乳胶小球或阳离子化铁蛋白（CF）的玻璃之间的相互作用，并将它们在腹面的组织情况与添加到已铺展在玻璃或福尔马膜网格上的血小板上时相同颗粒的命运进行了比较。血小板很容易在颗粒包被的玻璃表面铺展。在相互作用的早期阶段，Fgn/Au、CF和乳胶颗粒被开放小管系统（OCS）的通道摄取。Fgn/Au和CF常常通过OCS通道到达背面，然后被转移到血小板中心。相比之下，Fgn/Au、CF和乳胶层在铺展血小板的底面从边缘到边缘均匀分散。未观察到铺展血小板下方的颗粒从周边和中间区域向中心区域清除。除非铺展的细胞相互接触，颗粒不会从血小板边缘的上侧移动到下侧，也不会从边缘的腹面移动到上侧。因此，颗粒将OCS用作一条双向通道。铺展或正在铺展的血小板下方预先包被玻璃上Fgn/Au、CF或乳胶均匀分散层的持续存在表明，颗粒在自由上侧和结合下侧的处理方式存在显著差异。这些结果支持了这样的概念，即移动受体的主要目的是促进铺展，而下侧是一个受保护的粘附区域。
