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 m icroscopic 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 abund ant in the basolateral plasma membrane of outer hair cells (OHCs) in t he 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 i n a punctate pattern at 10 days after birth. Immunostaining intensity increased gradually and developed a linear pattern along the entire OH C basolateral plasmalemma between 10 and 16 days after birth when it a pproached adult levels. The developmental expression of GLUT 5 corresp onded with the appearance of glycogen in OHCs and structural maturatio n of the organ of Corti. This time period also coincided with the onse t and rapid maturation of auditory function in the gerbil. GLUT 5 appa rently supports OHC function by facilitating uptake of glucose which e nables these cells to sustain a high level of metabolic activity in a relatively anaerobic environment.