Takano K, Bogert M, Malamud D, Lally E, Hand A R
Department of Oral Histology, Nagasaki University School of Dentistry, Japan.
Anat Rec. 1991 Jul;230(3):307-18. doi: 10.1002/ar.1092300303.
The secretory granules of salivary glands often display complex internal substructures, yet little is known of the molecular organization of their contents or the mechanisms involved in packaging of the secretory proteins. We used post-embedding immunogold labeling with antibodies to two secretory proteins, agglutinin and alpha-amylase, to determine their distribution in the Golgi apparatus and secretory granules of the human submandibular gland acinar cells. With monoclonal antibodies specific for carbohydrate epitopes of the agglutinin, reactivity was found in the trans Golgi saccules, trans Golgi network, and immature and mature secretory granules. In the granules, labeling was seen in regions of low and medium electron density, but not in the dense cores. Reactivity seen on the apical and basolateral membranes of acinar and duct cells was attributed to a shared epitope on a membrane glycoprotein. Labeling with a polyclonal antibody to amylase was found in the Golgi saccules, immature and mature secretory granules, but not in the trans Golgi network. In the granules, amylase was present in the dense cores and in areas of medium density, but not in the regions of low density. These results indicate that these two proteins are distributed differently within the secretory granules, and suggest that they follow separate pathways between the Golgi apparatus and forming secretory granules. Small vesicles and tubular structures that labeled only with the antibodies to the agglutinin were observed on both faces of the Golgi apparatus and in the vicinity of the cell membrane. These structures may represent constitutive secretion vesicles involved in transport of the putative membrane glycoprotein to the cell membrane.
唾液腺的分泌颗粒常常呈现出复杂的内部亚结构，然而对于其内容物的分子组织以及分泌蛋白包装所涉及的机制却知之甚少。我们使用针对两种分泌蛋白（凝集素和α-淀粉酶）的抗体进行包埋后免疫金标记，以确定它们在人下颌下腺腺泡细胞的高尔基体和分泌颗粒中的分布。使用针对凝集素碳水化合物表位的单克隆抗体，在反式高尔基体扁平囊、反式高尔基体网络以及未成熟和成熟的分泌颗粒中发现了反应活性。在颗粒中，在低电子密度和中等电子密度区域可见标记，但在致密核心中未见。在腺泡细胞和导管细胞的顶端和基底外侧膜上观察到的反应活性归因于膜糖蛋白上的一个共同表位。用抗淀粉酶的多克隆抗体进行标记，在高尔基体扁平囊、未成熟和成熟的分泌颗粒中发现了标记，但在反式高尔基体网络中未发现。在颗粒中，淀粉酶存在于致密核心和中等密度区域，但不存在于低密度区域。这些结果表明这两种蛋白质在分泌颗粒内的分布不同，并提示它们在高尔基体和形成中的分泌颗粒之间遵循不同的途径。在高尔基体的两面以及细胞膜附近观察到仅用凝集素抗体标记的小泡和管状结构。这些结构可能代表参与将假定的膜糖蛋白转运到细胞膜的组成型分泌小泡。
