Expression and Localization of Glucose Transporters in Rodent Submandibular Salivary Glands

Abstract

Background/Aim: The submandibular gland is one of the three major salivary glands, producing a mixed secretion; this saliva is hypotonic compared to plasma. It also secretes glucose, but the mechanisms responsible for this process are poorly understood. Our study addressed the question whether glucose transporters are expressed and how are they localized within specific rodent submandibular cells, in order to estimate a possible implication in salivary glucose disposal. Methods: Immunohistochemistry, RT-qPCR and Western blotting were performed to determine the presence/localization of glucose transporters in rodent submandibular glands. Results: GLUT4 was identified in the submandibular salivary gland at both mRNA and protein level. The immunohistochemical analysis revealed its localization preponderantly in the ductal cells of the gland, near to the basolateral. SGLT1 and GLUT1 were highly expressed in submandibular tissues in both acinar and ductal cells, but not GLUT2. These results were confirmed by RT-qPCR. It was also documented that insulin stimulates the net uptake of D-glucose by ductal rings prepared from submandibulary salivary glands, the relative magnitude of such an enhancing action being comparable to that found in hemidiaphragms. Conclusion: At least three major glucose transporters are expressed in the rodent submandibular glands, of which GLUT4 is specifically localized near the basolateral side of ductal structures. This points-out its possible role in regulating glucose uptake from the bloodstream, most likely to sustain ductal cellular metabolism.

Keywords

• GLUT1
• GLUT2
• GLUT4
• SGLT1
• Submandibular salivary gland
• Glucose transporters
• Ductal cell