Lotti L V, Hand A R
Clinical Investigations and Patient Care Branch, National Institute of Dental Research, Bethesda, Maryland 20892.
Cell Tissue Res. 1989 Feb;255(2):333-42. doi: 10.1007/BF00224116.
The ability of duct cells of the rat parotid gland to internalize bovine serum albumin (BSA) and several glycosylated albumins (glucosamide, galactosamide, fucosamide, lactosyl, p-aminophenyl-N-acetyl-D-glucosamide, p-aminophenyl-N-acetyl-D-mannopyranoside, p-aminophenyl-N-acetyl-D-galactosamide) was investigated. The various BSA preparations were infused into the gland via the main excretory duct, after which the tissues were fixed and prepared for light and electron microscopy. Immunolocalization of native BSA, as well as the glycosylated BSAs, was performed on thin sections, using an unlabeled antibody to BSA followed by protein A-colloidal gold. Gold particles were present over the lumina of both intercalated ducts and striated ducts, and over small endocytic structures and large vacuoles in the apical cytoplasm of both duct cell types. Endocytosis of the glycosylated BSAs by duct cells was greater than native BSA. Fucosylamide-BSA and mannopyranoside-BSA was taken up to a greater extent than the other glycosylated BSAs. Uptake by intercalated duct cells was greater than by striated duct cells, was independent of the concentration of the glycosylated BSA, and was reduced by an excess of the corresponding sugar. Striated duct cells showed some damage by the glycosylated BSAs that was concentration-dependent, and which was reduced in the presence of an excess of the corresponding sugar. These results suggest that endocytosis by salivary gland duct cells may involve specific recognition of carbohydrate residues and that the endocytosis of acinar secretory proteins observed in certain conditions may be due to increased and/or altered protein glycosylation.
研究了大鼠腮腺导管细胞内化牛血清白蛋白（BSA）和几种糖基化白蛋白（葡糖胺、半乳糖胺、岩藻糖胺、乳糖基、对氨基苯基 - N - 乙酰 - D - 葡糖胺、对氨基苯基 - N - 乙酰 - D - 甘露吡喃糖苷、对氨基苯基 - N - 乙酰 - D - 半乳糖胺）的能力。将各种BSA制剂通过主排泄导管注入腺体，之后将组织固定并制备用于光镜和电镜观察。使用抗BSA的未标记抗体和蛋白A - 胶体金，对薄切片进行天然BSA以及糖基化BSA的免疫定位。闰管和纹状管的管腔内以及两种导管细胞类型顶端细胞质中的小内吞结构和大液泡上均存在金颗粒。导管细胞对糖基化BSA的内吞作用大于天然BSA。岩藻糖胺 - BSA和甘露吡喃糖苷 - BSA比其他糖基化BSA的摄取程度更高。闰管细胞的摄取大于纹状管细胞，与糖基化BSA的浓度无关，并且过量的相应糖类会使其摄取减少。纹状管细胞受到糖基化BSA的一些损伤，这种损伤呈浓度依赖性，并且在存在过量相应糖类的情况下会减轻。这些结果表明，唾液腺导管细胞的内吞作用可能涉及对碳水化合物残基的特异性识别，并且在某些情况下观察到的腺泡分泌蛋白的内吞作用可能是由于蛋白质糖基化增加和/或改变所致。
