White J G
Department of Laboratory Medicine, University of Minnesota Medical School, Minneapolis 55455.
Arterioscler Thromb. 1993 Aug;13(8):1236-43. doi: 10.1161/01.atv.13.8.1236.
Mobile receptors on surface- and suspension-activated platelets bind a variety of specific and nonspecific antigens and particulates and clear them from the plasma membrane to channels of the open canalicular system (OCS). The present study examined the interaction of platelets with latex spherules of increasing size to identify the role of mobile receptors and binding sites in hemostatic physiology. Small latex spherules 0.09 to 3.13 microns in average diameter were cleared from peripheral margins to central zones and the OCS on surface-activated platelets and from the surface membrane to the OCS of platelets in suspension. Larger spheres, 6.4 microns in diameter, could not be moved across the membranes of solid phase- and fluid phase-activated platelets. Instead, platelets moved their surface membranes through the contact sites fixed on the surface of immobile spheres, bringing interior membranes of the OCS channels to the latex. This change, in which mobile membranes move through fixed contact sites rather than mobile receptor complexes moving across plasma membranes, results in evagination of almost all OCS channels on large latex spherules. A similar mechanism may be involved in the interaction of platelets with relatively flat surfaces, such as denuded subendothelium.
表面激活和悬浮激活的血小板上的移动受体可结合多种特异性和非特异性抗原及颗粒，并将它们从质膜清除至开放管道系统（OCS）的通道。本研究检测了血小板与尺寸不断增大的乳胶小球之间的相互作用，以确定移动受体和结合位点在止血生理学中的作用。平均直径为0.09至3.13微米的小乳胶小球从外周边缘被清除至表面激活血小板的中央区域和OCS，以及从悬浮血小板的表面膜被清除至OCS。直径为6.4微米的较大球体无法穿过固相激活和液相激活血小板的膜。相反，血小板通过固定在不动球体表面的接触位点移动其表面膜，将OCS通道的内膜带到乳胶处。这种变化，即移动膜通过固定接触位点移动，而不是移动受体复合物穿过质膜移动，导致大乳胶小球上几乎所有OCS通道外翻。血小板与相对平坦表面（如裸露的内皮下层）的相互作用可能涉及类似机制。
