Immunohistochemical localization of neurotrophins and neurotrophin receptors in human and mouse salivary glands.

This study was undertaken to analyze the occurrence of low- (p75) and high-affinity (TrkA, TrkB and TrkC) neurotrophin receptor proteins in human and mouse salivary glands using immunohistochemistry. Furthermore, the presence of neurotrophins was also investigated. The study was carried out on 14 human (4 parotid, 6 submandibular and 4 sublingual glands) and 5 mouse salivary glands, using polyclonal antibodies against Trk proteins. The intensity of immunostaining was calculated automatically and evaluated in arbitrary units of grey levels. In human tissues no immunoreactivity (IR) for the assessed antigens was observed in the serous or mucous acinar cells, although TrkA IR was found in the acini of the submandibular gland. The cells of the intercalated ducts showed p75 IR (sublingual) and TrkA IR (parotid gland). The striated and excretory ducts displayed p75 IR, TrkA IR and TrkC IR in all glands, but TrkB IR was never detected. No neurotrophins were detected. In the mouse glands the ductal cells display IR for p75 (submandibular) and Trks A and C (parotid and submandibular) but not the sublingual gland. Acinar cells of the submandibular gland also show p75 IR. The only neurotrophin found in the mouse salivary glands was NGF (submandibular gland). These results suggest that neurotrophins may be involved in controlling the physiology of epithelial salivary cells.