The cytoskeleton of Clara cell mammalian lung

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Previously, the author reported the presence of abundant filaments in apical cytoplasmic protrusions (apical caps) of Clara cells of rats by perfusing their lungs with a medium containing Triton X-100 solution. This finding suggested that the apical cap was quint stable structure and was not apocrine droplet. Clara cells were widely distributed in the terminal bronchioles and in the upper airway and have the important role for the secretion of proteinous materials or oxidative metabolism of xenobiotics. The presence of filaments were investigated in several mammals and the nature and the genesis of the filaments were studied in rat lung.Filaments were found in apical caps of Clara cells of ret, mouse, guinea pig, hamster, steer, pig and human lung. The presence of these filaments can be utilized for identifying nonciliated bronchiolar epithelial cells in each airway. These filaments were in close association with cell membrane and formed homogeneous matrix just under the cell membrance … More .Human Clara cell with few smooth-surfaced endoplasmic reticulum have abundant filaments such as rat or mouse Clara cells.Most of these filaments were found to be actin by the use of heavy meromyosin (HMM). Some filaments which were not decorated with HMM were shown to be cytokeration by immunohistochemical method. Desmin, vimentin, neurofilament and GFAP were not found.The presence of filaments were investigated in pre- and postnatal rat. Clara cells of fetuses at the late gestation were distinguished from ciliated cells and contained a large amount of glycogen in the cytoplasm. After detergent treatment, filaments were not found in the cytoplasm. However, glycogen began to decrease rapidly and the presence of filaments was confirmed in the cell of a 1-day old rat. It has been shown that Clara cells are immature at birth and undergo marked early postnatal maturation. The present results suggest that the appearance of filaments also relates to the maturation of Clara cells and the release of granules. Less