Postnatal expression of the facilitated glucose transporter, GLUT 5, in gerbil outer hair cells.

The fifth isoform from the family of facilitative glucose transporters (GLUT 5) was identified in the gerbil cochlea by light and electron microscopic immunohistochemistry. The immunostaining procedure employed a polyclonal antibody raised against a synthetic peptide representing the carboxy terminus of human GLUT 5. Immunoreactive GLUT 5 was abundant in the basolateral plasma membrane of outer hair cells (OHCs) in the mature gerbil cochlea. No immunostaining was observed in any other site in the cochlea or vestibular system. During postnatal development of the gerbil inner ear, OHCs were first observed to express GLUT 5 in a punctate pattern at 10 days after birth. Immunostaining intensity increased gradually and developed a linear pattern along the entire OHC basolateral plasmalemma between 10 and 16 days after birth when it approached adult levels. The developmental expression of GLUT 5 corresponded with the appearance of glycogen in OHCs and structural maturation of the organ of Corti. This time period also coincided with the onset and rapid maturation of auditory function in the gerbil. GLUT 5 apparently supports OHC function by facilitating uptake of glucose which enables these cells to sustain a high level of metabolic activity in a relatively anaerobic environment.