Hemoterapia-Hemostasia, CDB, Hospital Clínic, IDIBAPS, Universitat de Barcelona.
Platelets. 2010;21(8):658-66. doi: 10.3109/09537101003716200. Epub 2010 Oct 19.
Studies in animal models are useful to understand the basic mechanisms involved in hemostasis and the functional differences among species. Ultrastructural observations led us to predict differences in the activation and secretion mechanisms between equine and human platelets. The potential mechanisms involved have been comparatively explored in the present study. Equine and human platelets were activated with thrombin (0.5 U/ml) and collagen (20 µg/ml), for 90 seconds, and samples processed to evaluate: i) ultrastructural changes, by electron microscopy, ii) actin polymerization and cytoskeletal assembly, by polyacrylamide gel electrophoresis, and iii) specific molecules involved in activation and secretion, by western blot. In activated human platelets, centralization of granules, cytoskeletal assembly and fusion of granules with the open canalicular system were observed. In activated equine platelets, granules fused together forming an organelle chain that fused with the surface membrane and released its content directly outside the platelets. Human platelets responded to activation with actin polymerization and the assembly of other contractile proteins to the cytoskeleton. These events were almost undetectable in equine platelets. When exploring the involvement of the synaptosomal-associated protein-23 (SNAP-23), a known regulator of secretory granule/plasma membrane fusion events, it was present in both human and equine platelets. SNAP-23 was shown to be more activated in equine platelets than human platelets in response to activation, especially with collagen. Thus, there are significant differences in the secretion mechanisms between human and equine platelets. While in human platelets, activation and secretion of granules depend on mechanisms of internal contraction and membrane fusion, in equine platelets the fusion mechanisms seem to be predominant.
动物模型研究有助于理解止血过程中的基本机制和物种之间的功能差异。超微结构观察使我们能够预测马和人血小板之间的激活和分泌机制的差异。本研究比较探讨了潜在的机制。用凝血酶（0.5 U/ml）和胶原蛋白（20 μg/ml）激活马和人血小板 90 秒，并处理样本以评估：i）电子显微镜下的超微结构变化，ii）肌动蛋白聚合和细胞骨架组装，iii）通过 Western blot 评估参与激活和分泌的特定分子。在激活的人血小板中，观察到颗粒的中心化、细胞骨架的组装以及颗粒与开放小管系统的融合。在激活的马血小板中，颗粒融合在一起形成一个细胞器链，与质膜融合并直接将其内容物释放到血小板外。人血小板对激活的反应是肌动蛋白聚合和其他收缩蛋白向细胞骨架的组装。这些事件在马血小板中几乎无法检测到。当探索突触相关蛋白-23（SNAP-23）的参与时，SNAP-23 是一种已知的调节分泌颗粒/质膜融合事件的蛋白，在人和马血小板中都存在。与人类血小板相比，SNAP-23 在马血小板中对激活的反应更为活跃，尤其是与胶原蛋白。因此，人血小板和马血小板之间的分泌机制存在显著差异。在人血小板中，颗粒的激活和分泌依赖于内部收缩和膜融合机制，而在马血小板中，融合机制似乎更为重要。
