Ultrastructural changes in aging rat tracheal gland.

Ultrastructural differences in the tracheal gland between young and aged rats were studied. Marked differences were observed in the serous cells between the young (8-17 week-old) and the aged (20-30 month-old) subjects. The secretory granules of the serous cells of the young subjects were homogeneously electron dense, whilst those of the aged subjects had a bizonal appearance. These bizonal granules contained abundant mucous material. The trans Golgi network of the aged rat serous cells was more developed and formed a fine meshwork in comparison with that of the young subjects. In the aged subjects, findings indicate alterations not only in the function of the Golgi apparatus including formation of secretory granules and addition of terminal sugars to the secretory protein but also the histochemical and ultrastructural properties of the secretory material. The changes in the Golgi apparatus are possibly responsible for depression of the tracheal host defense mechanism and might explain why various airway diseases increase with aging.