Young S L, Fram E K, Randell S H
Am Rev Respir Dis. 1986 May;133(5):899-907.
We have employed three-dimensional reconstructions and cytochemistry to analyze nonciliated bronchiolar epithelial (Clara) cells from rat lungs. We identified a previously unreported ovoid granule type, which was characterized by its relative electron-lucency and eccentric electron-dense core. These electron-lucent granules were less common than electron-dense granules and were polarized toward the Golgi. They occupied 0.51% of the cell volume. Quantitative analysis of cell volume fractions showed the more numerous electron-dense granules to be polarized toward the air border; they occupied 2.5% of the cell volume. Periodic acid-thiocarbohydrazide-silver protein staining for hexose sugars indicated no differences between the granule types with regard to their carbohydrate content. Multivesicular bodies occupied 0.42% of total cell volume and were distinctly polarized toward the surface of the Golgi. Rod-shaped granules were present in 4 of the 6 reconstructed cells, ranging in number from 0 to 9 per cell. Nine apparent secretory events were seen in 6 cells and all appeared as exocytosis. We conclude that rat Clara cells contain at least 3 morphologically distinct granule types located in different volumes of the cell, and that exocytosis is the mode of secretion. The functional relationship between the ovoid granule types could include precursor-product lineage or different secretory products. We suggest that multivesicular bodies and light granules are stages in dark granule genesis.
我们采用三维重建和细胞化学方法分析了大鼠肺脏的无纤毛细支气管上皮（克拉拉）细胞。我们鉴定出一种先前未报道过的卵圆形颗粒类型，其特征是相对电子透明且有偏心的电子致密核心。这些电子透明颗粒比电子致密颗粒少见，且向高尔基体极化。它们占细胞体积的0.51%。细胞体积分数的定量分析表明，数量较多的电子致密颗粒向气界极化；它们占细胞体积的2.5%。对己糖进行的高碘酸-硫代碳酰肼-银蛋白染色显示，这两种颗粒类型在碳水化合物含量方面没有差异。多囊体占细胞总体积的0.42%，并明显向高尔基体表面极化。在6个重建细胞中的4个细胞中存在杆状颗粒，每个细胞中的数量从0到9不等。在6个细胞中观察到9次明显的分泌事件，均表现为胞吐作用。我们得出结论，大鼠克拉拉细胞含有至少3种形态上不同的颗粒类型，位于细胞的不同区域，且胞吐作用是分泌方式。卵圆形颗粒类型之间的功能关系可能包括前体-产物谱系或不同的分泌产物。我们认为多囊体和轻颗粒是暗颗粒形成过程中的阶段。
