Cytochemical characterization of the myoepithelial cells in palatine glands.

Myoepithelial cells of rat and mouse palatine glands are similar in fine structural appearance to those of other exocrine glands and smooth muscle cells. Myoepithelial cells reveal fibrils, and vesicular structures comparable to pinocytic or surface vesicles of smooth muscle cells. Lanthanum-impregnated preparations of the gland reveal that many of these vesicle-like structures are, in fact, invaginations of the plasma membrane and are continuous with the extracellular space. Observations on glandular tissue incubated for the demonstration of ATPase and adenylate cyclase have indicated that a high level of activity of these two enzymes is localized in the plasma membrane of the myoepithelial cells facing the acinar cells, and in vesicular structures along this membrane. The possibility that these enzyme activities are related to contractility of myoepithelial cells is discussed.