Endothelin expression in salivary gland

The present paper reviews the roles of endothelin (ET) in the rat submandibular gland (SMG). ET and its mRNA are expressed in the granular convoluted tubule (GCT) segment by immunostaining and in situ hybridization, respectively. ET is synthesized in granular cells of the GCT segment, stored in secretory granules, and secreted into the oral cavity. It is well known that granular cells in the GCT segment of the SMG in mice and rats express many kinds of growth factor such as epidermal growth factor and nerve growth factor. These growth factors are discharged into saliva and thought to regulate oral-esophageal and gastrointestinal mucosa. ET acts as a potent vasoconstrictor with mitogenic property and is excreted from Weibel-Palade bodies in vascular endothelial cells. ET in the salivary origin may regulate its own functions as noted in the endothelial origin. This review deals with comparative discussion of ET and other growth factors, which originate from GCT segments in rodents.