Cholecystokinin- and Melatonin-receptors in human and rat salivary glands

Recent observations of ours show the rat parotid gland to respond, in vivo, to gastrin, cholecystokinin and melatonin with protein secretion, without any accompanying overt fluid secretion. Moreover, we do also find pieces of human parotid tissue to secrete protein in vitro and to display ultrastructural changes associated with secretory activity. OBJECTIVES: To visualize the receptor-substrate for the action of these hormones in parotid, submandibular and sublingual glands of humans and rats. METHODS: Immunochemistry was applied, using antibodies for cholecystokinin (CCK)-A, CCK-B and melatonin 2-receptors (including negative controls). The sections were examined under light microscopy. The specimens from humans were obtained at benign salivary gland surgery (15 patients), while glands of 8 rats of both sexes were used. RESULTS: The pattern of immunoreactivity was similar in humans and rats. In all types of glands, the acinar serous cells (but not the mucous cells) and the striated duct cells stained for the three receptors under study. The staining for CCK-A receptors of acinar cells was stronger than for duct cells, while the opposite was the case for the two other receptors. CONCLUSION: A hormonal influence on the secretory activity of salivary glands may be a general phenomenon. In response to a meal, the glands are probably not only regulated by the well-known cephalic phase (nerves) but also by a gastric (gastrin) and an intestinal phase (cholecystokinin and melatonin), the three phases overlapping each other