Endocytosis in alveolar type II cells: effect of charge and size of tracers.
Endocytosis in alveolar type II cells: effect of charge and size of tracers.
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DOI：
10.1073/pnas.81.19.6054
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发表时间：
1984-10
影响因子：
11.1
通讯作者：
M. Williams
中科院分区：
文献类型：
--
作者：
M. Williams
用电子显微镜研究了成年大鼠肺泡上皮的II型细胞，以确定其内吞不同分子电荷和大小的电子密度示踪剂的能力。所研究的示踪剂是天然（阴离子）铁蛋白、阳离子铁蛋白、70千道尔顿葡聚糖和胶体碳。肺泡巨噬细胞大量摄取所有示踪剂，而II型细胞仅大量摄取阳离子铁蛋白。该示踪剂依次出现在小的胞泡、大的电子透光多泡体、小的电子致密多泡体中，并在注射后30分钟出现在片层体的非片层基质中。到2小时，任何标记细胞的所有片层体都含有阳离子铁蛋白。阳离子铁蛋白似乎也可以通过II型细胞的囊泡从肺泡转运到间质，而不是通过I型细胞。天然铁蛋白和葡聚糖在与阳离子铁蛋白相同的细胞器中被观察到，但数量要少得多；胶体碳不被II型细胞吸收。这些示踪剂未在肺泡间质中观察到。因此，II型细胞似乎优先内化与细胞膜结合的示踪剂。一旦进入细胞内，示踪剂可能进入一条终止于片层体的途径，或者在阳离子铁蛋白的情况下，可能被运送穿过细胞。
The type II cell of the alveolar epithelium of adult rats has been studied by electron microscopy to determine its ability to endocytose electron-dense tracers of differing molecular charge and size. The tracers studied were native (anionic) ferritin, cationic ferritin, 70-kilodalton dextran, and colloidal carbon. Alveolar macrophages ingested all tracers in large amounts, while type II cells took up significant amounts of cationic ferritin only. This tracer was observed, in sequence, within small pinocytic vesicles, large electron-lucent multivesicular bodies, small electron-dense multivesicular bodies, and, by 30 min after instillation, within the nonlamellar matrix of lamellar bodies. By 2 hr all lamellar bodies in any labeled cell contained cationic ferritin. Cationic ferritin also appeared to be transported from alveoli to interstitium by vesicles of type II, but not type I, cells. Native ferritin and dextran were observed in the same organelles as cationic ferritin but in much smaller amounts; colloidal carbon was not taken up by type II cells. These tracers were not observed in the alveolar interstitium. Type II cells therefore appear to internalize preferentially the tracer that binds to the cell membrane. Once within the cell, the tracer may enter a pathway that terminates in a lamellar body or, in the case of cationic ferritin, may be ferried across the cell.