Wasano K, Hirakawa Y
Department of Anatomy, Faculty of Medicine, Kyushu University, Fukuoka, Japan.
Histochemistry. 1994 Nov;102(5):329-35. doi: 10.1007/BF00268903.
Alveolar type 2 cells are known to take up surfactant phospholipids and proteins from the alveolar space and recycle them into secretory organelles via a receptor-mediated endocytic pathway. To clarify the intracellular route(s) through which materials ingested by the cells are processed, we examined the immunocytochemical localization of late endosomal and lysosomal membrane markers, rab 7 and lamp 1 proteins, within rat alveolar type 2 cells. The limiting membranes of lamellar bodies (LBs) showed positive immunoreactivity for both proteins, whereas multivesicular bodies (MVBs) exhibited positive immunoreactivity only for lamp 1 protein on free vesicles in the MVB lumen. From these findings, it is suggested that LBs are not only secretory granules, but also constitute one of the late endosomal compartments of the cells and that MVBs of this cell type may be targeted to cell organelle(s) other than lysosomes.
已知肺泡Ⅱ型细胞可从肺泡腔摄取表面活性物质磷脂和蛋白质，并通过受体介导的内吞途径将它们循环至分泌细胞器。为了阐明细胞摄取的物质所经过的细胞内途径，我们检测了大鼠肺泡Ⅱ型细胞内晚期内体和溶酶体膜标志物（rab 7和lamp 1蛋白）的免疫细胞化学定位。板层小体（LB）的界膜对这两种蛋白均显示阳性免疫反应，而多囊泡体（MVB）仅对MVB管腔内游离囊泡上的lamp 1蛋白呈阳性免疫反应。从这些发现推测，LB不仅是分泌颗粒，还构成细胞晚期内体区室之一，且这种细胞类型的MVB可能靶向除溶酶体之外的其他细胞器。
