Mitosis and hypertrophy of intercalated duct cells and endothelial cells in the isoproterenol-treated rat parotid gland.

Chronic treatment of rats with isoproterenol (IPR) induces mitosis and differentiation of intercalated duct cells, and mitosis and hypertrophy of endothelial cells of the microvasculature in the parotid gland. Mitoses occurred in duct cells situated at or near the acinar-intercalated duct junction, and were most numerous after six IPR injections. These cells increased in size, contained numerous electron-lucent granules, and were incorporated into the hypertrophic acini. The granules contained branching filamentous or finely reticulated material, and did not react with histochemical stains for carbohydrate. Capillary and venule endothelial cell mitoses were frequently seen after four to six IPR injections. The endothelial cells increased in thickness, contained abundant cytoplasmic organelles, lacked fenestrations, and had few pinocytotic vesicles. These results demonstrate the extensive nature of the response to chronic IPR treatment, and are consistent with the concept that the intercalated ducts have an important role in salivary gland physiology.