Presence of fructose transporter GLUT5 in the S3 proximal tubules in the rat kidney

Presence of fructose transporter GLUT5 in the S3 proximal tubules in the rat kidney.BackgroundFructose is a nutrient as well as a potent agent for the formation of advanced glycation end product in diabetes. GLUT5 is a facilitated-diffusion fructose transporter expressed in the small intestine and kidney. Previous reports on the localization of GLUT5 by in situ hybridization and immunohistochemistry were controversial.MethodsThe expression of GLUT5 was checked by reverse transcription-polymerase chain reaction and Southern blotting and immunoblotting analyses. Localization of GLUT5 was visualized by high-resolution immunofluorescence and immunogold electron microscopy.ResultsWe were able to confirm the expression of GLUT5 in the kidney. GLUT5 was predominantly present in the outer stripe of the outer medulla, where it was localized in the S3 proximal tubule cells. Double labeling with phalloidin showed that GLUT5 was localized in the brush border of the S3 proximal tubule cells. Ultrastructural examination revealed that GLUT5 was present along the plasma membrane of the apical microvilli.ConclusionGLUT5 is present at the apical plasma membrane of S3 proximal tubule cells and may serve as the transporter of fructose