IMMUNOHISTOCHEMICAL LOCALIZATION OF BRAIN-TYPE GLUCOSE-TRANSPORTER IN MAMMALIAN INNER EARS - COMPARISON OF DEVELOPMENTAL AND ADULT STAGES

Inner ears from five mammalian genera were examined immunohistochemically with a rabbit polyclonal antiserum against the brain type glucose transporter (GLUT1). Vascular endothelial cells distributed widely in soft tissues of the cochlea and vestibular system in all five genera showed uniform immunostaining. The basal cell layer of the stria vascularis also contained GLUT1 in all genera, and in the guinea pig, the strial marginal cells reacted as well. GLUT1 was expressed in satellite cells surrounding spiral ganglion neurons but only in the gerbil and cat. In the developing inner ear of the gerbil, endothelial cells expressed GLUT1 at 2 days after birth, the earliest stage examined. Immunoreactive transporter also was detected at this time in cells lying under strial marginal cells and interpreted as immature basal cells. Satellite cells acquired affinity for GLUT1 antibody between days 12 and 16 after birth. The expression of GLUT1 by the various cell types correlates well with their structural and functional maturation. GLUT1 apparently plays a role in glucose transport in the inner ear where it mediates efflux from blood vessels into perilymph. It also appears to facilitate uptake of glucose by the stria vascularis from interstitial fluid via the basal cell layer and, in some species, by spiral ganglion neurons through satellite cells.