Spatial characterization of the phoenixin receptor in the lacrimal and major salivary glands

Objective: To identify and characterize the expression of phoenixin receptor GPR173 (G protein-coupled receptor 173) in the rat lacrimal and major salivary glands (parotid, submandibular, and sublingual). GPR173 is associated with hormonal regulation and autoimmunity; however, its expression in exocrine glands has yet to be characterized. Design: Under anesthesia, eight Sprague Dawley rats underwent bilateral dissection of the lacrimal and major salivary glands. GPR173 expression was assessed using Western blotting and immunofluorescence. Immunoreactivity was quantified using ImageJ software and compared using the Friedman test with DunnBonferroni post hoc analysis. Results: GPR173 protein expression was found in all examined exocrine glands. In the major salivary glands, GPR173 was detected in both acinar and ductal cells, while expression was confined to acinar cells in the lacrimal gland. The submandibular and parotid glands showed significantly higher immunoreactivity than the lacrimal gland (p < .01 and p < .05, respectively). Ductal epithelium showed stronger immunopositivity compared to acinar epithelium. GPR173 immunoreactivity was also observed in periductal stromal tissue in major salivary glands. Conclusion: GPR173 expression was observed in both acinar and ductal cells of all major salivary glands, while in the lacrimal gland, it was restricted to the acinar cells. This differential localization suggests tissue-specific relevance.