White J G, Burris S M
Am J Pathol. 1984 Jun;115(3):412-7.
Blood platelets have a characteristic discoid shape supported by a circumferential band of microtubules. Following stimulation by aggregating agents or foreign surfaces, platelets lose their discoid form, extend pseudopods, and undergo a process of internal reorganization. Randomly dispersed cytoplasmic organelles become concentrated in cell centers within rings of microtubules and masses of microfilaments. Questions have been raised about this process and its contractile nature by studies demonstrating that platelet microtubules dissolve within seconds after activation and reassemble several minutes later in new locations. Earlier investigations showed that Taxol, a microtubule-stabilizing agent, did not inhibit platelet shape change, internal transformation, secretion, aggregation, or clot retraction. In the present study the diameters of microtubule coils in discoid platelets treated or not treated with Taxol and in platelets activated by thrombin, ADP, and a foreign surface were measured. The results of the study reveal no significant differences in diameters of microtuble rings in control or Taxol-treated cells. However, after activation by ADP, thrombin, or the grid surface, the diameter of coiled microtubules decreased by 30% or more. The results support the concept that internal transformation is a contractile event.
血小板具有由微管的圆周带支撑的特征性盘状形状。在受到聚集剂或异物表面刺激后，血小板失去其盘状形态，伸出伪足，并经历内部重组过程。随机分散的细胞质细胞器集中在微管环和微丝团内的细胞中心。通过研究表明血小板微管在激活后几秒钟内溶解并在几分钟后在新位置重新组装，人们对这一过程及其收缩性质提出了疑问。早期研究表明，微管稳定剂紫杉醇并不抑制血小板形状变化、内部转化、分泌、聚集或凝块收缩。在本研究中，测量了用或不用紫杉醇处理的盘状血小板以及由凝血酶、ADP和异物表面激活的血小板中微管盘绕的直径。研究结果显示，对照或紫杉醇处理的细胞中微管环的直径没有显著差异。然而，在被ADP、凝血酶或网格表面激活后，盘绕微管的直径减少了30%或更多。这些结果支持了内部转化是一个收缩事件的概念。
