Tuft cells in the main excretory duct epithelia of the three major rat salivary glands.

We report the tuft cells in the main excretory duct epithelia of rat salivary glands. These cells exhibit similar fundamental characteristics in the salivary glands and in other organs. However, numerous membrane-bound electron-dense granules are present among the microvilli of the tuft cells in the submandibular gland, but not in other organs. The apical cytoplasm contains numerous vesicles with a filamentous substance that reacts positively for glycoconjugates. The vesicles frequently are close to the apical plasma membrane and seem to open into the lumen. Nerve endings with synaptic vesicles are seen close to the basal portion of the tuft cells. The ratio of the tuft cells to principal cells is highest in the submandibular gland and lowest in the sublingual gland. The functions of the tuft cells in the salivary glands are suggested to be secretion, absorption, and reception.