Adeghate E, Donáth T
1st Department of Anatomy, Semmelweis University, Medical School, Budapest, Hungary.
Gegenbaurs Morphol Jahrb. 1989;135(5):697-704.
The mechanism of secretory granule formation and exocytosis in the endocrine cells of normal and transplanted rat pancreas was studied using electron microscopy. On the one hand, formation of secretory granules starts with the dilatation of the 2 ends or the vesicularization of the middle parts of rough endoplasmatic reticulum (RER). On the other hand, prohormone ribosomes condense into the vesicles of the GOLGI apparatus. This probably indicates that the GOLGI complex is not the only source of formation of secretory granules. Exocytosis occurs with the formation of an electron dense streak between the perigranular membrane and the apical cell membrane. This is followed by the rupture of the streak at this midpoint allowing the granule to extrude into the space between the cell membrane and the parenchymal basal membrane. This fusion-rupture-extrusion mechanism repeats itself at the parenchymal and capillary basal membranes and also at the endothelium until it gets into the capillary lumen, showing that hormones of pancreatic endocrine cells may be actively transported into circulation as intact secretory granules. There is no significant morphological difference between the mechanism of secretory granule formation in normal and transplanted pancreatic tissue.
利用电子显微镜研究了正常和移植大鼠胰腺内分泌细胞中分泌颗粒形成和胞吐作用的机制。一方面，分泌颗粒的形成始于粗面内质网（RER）两端的扩张或中间部分的囊泡化。另一方面，激素原核糖体凝聚到高尔基体的囊泡中。这可能表明高尔基体复合体并非分泌颗粒形成的唯一来源。胞吐作用发生时，在颗粒周围膜和顶端细胞膜之间形成一条电子致密带。随后这条带在中点处破裂，使颗粒挤出到细胞膜与实质基底膜之间的空间。这种融合 - 破裂 - 挤出机制在实质和毛细血管基底膜以及内皮处重复进行，直到进入毛细血管腔，这表明胰腺内分泌细胞的激素可能作为完整的分泌颗粒被主动转运到循环中。正常和移植胰腺组织中分泌颗粒形成机制在形态学上无显著差异。
