Chi E Y, Lagunoff D, Koehler J K
Proc Natl Acad Sci U S A. 1976 Aug;73(8):2823-7. doi: 10.1073/pnas.73.8.2823.
Within seconds after exposure of rat peritoneal mast cells to polymyxin B, bulges appear on the surface of the cells. Freeze-fracture electron microscopy reveals that each bulge overlies a mast cell granule. In contrast to the even distribution of intramembranous particles in the plasma membrane of unstimulated cells, the intramembranous particles in the stimulated cells are unevenly distributed in the membrane of the bulges with large patches of membrane lacking intramembranous particles. The membranes over the most prominent bulges are entirely free of intramembranous particles, and in some instances there is an increased concentration of intramembranous particles at the margins of the bulges. Perigranule membranes exhibit the same changes in distribution of intramembranous particles. Electron microscopy of thin sections of rapidly fixed, stimulated mast cells shows a peculiar structure of the membrane overlying some bulges; instead of the pentalaminar membranes previously demonstrated, the membrane at these sites of presumptive fusion of perigranule and plasma membrane assumes the form of a single dense lamina with a fine fuzzy coating on either side. It seems possible that membrane fusion and subsequent pore formation proceed in the stimulated mast cell through a stage of flight of intramembranous particles and molecular rearrangement of the other membrane components.
大鼠腹膜肥大细胞暴露于多粘菌素B后数秒内，细胞表面就会出现凸起。冷冻断裂电子显微镜显示，每个凸起都覆盖着一个肥大细胞颗粒。与未受刺激细胞的质膜中膜内颗粒均匀分布不同，受刺激细胞中的膜内颗粒在凸起的膜中分布不均，有大片膜区域缺乏膜内颗粒。最突出凸起上方的膜完全没有膜内颗粒，在某些情况下，凸起边缘的膜内颗粒浓度增加。颗粒周围膜在膜内颗粒分布上也表现出相同的变化。对快速固定的受刺激肥大细胞的超薄切片进行电子显微镜观察，发现覆盖一些凸起的膜具有特殊结构；在这些假定的颗粒周围膜与质膜融合部位，膜不是先前显示的五片层膜，而是呈现为单一致密薄片的形式，两侧有精细的模糊涂层。在受刺激的肥大细胞中，膜融合及随后的孔形成似乎可能通过膜内颗粒的逸出和其他膜成分的分子重排阶段进行。
