Expression of Glial Cell Line-Derived Neurotrophic Factor in Myoepithelial Cells of Mouse Tongue Salivary Glands

ganglion neurons4), and peripheral autonomic neurons5). GDNF mRNA is expressed in various parts of the developing central nervous system and peripheral tissues including the kidneys, teeth and skeletal muscles6). In particular, an abundant expression of GDNF mRNA is indicated in the smooth muscle layers of the intestine during embryogenesis7). Myoepithelial cells are found close to the acini and the intercalated ducts in the salivary glands, occupying the space between the basement membrane and basal plasma membrane of secretory epithelial cells, and are very similar to smooth muscle cells because of the presence of actin and myosin filaments in their cytoplasm and their ability to contract. Here we immunocytochemically found GDNF expression in the cells surrounding the acini and ducts of the lingual salivary glands, which we presumed to be myoepithelial cells. We therefore compared GDNF-positive cells with the cells stained by phalloidin, which labels F-actin. GDNF is shown to interact with a specific cell-surface receptor, GFRα1, and its biological effects are mediated through the interaction of GDNF, GFRα1, and a tyrosine kinase receptor, Ret8) . We therefore additionally examined the expression of GFRα1 and Ret in the lingual salivary glands using an immunocytochemical method.