NA,K-ATPASE ALPHA-SUBUNIT AND BETA-SUBUNIT ISOFORM DISTRIBUTION IN THE RAT COCHLEAR AND VESTIBULAR TISSUES

The distribution of five Na,K-ATPase subunit isoforms (alpha(1), alpha (2), alpha(3), beta(1), and beta(2)) in rat cochlear and vestibular ti ssues was determined by immunocytochemical techniques using subunit is oform specific polyclonal antibodies. The expression of Na,K-ATPase al pha and beta subunit isoforms varied among different cell regions of t he inner ear. The alpha(1) subunit isoform was more extensively distri buted in all inner ear tissues than the alpha(2) or alpha(3) subunit i soforms. The beta(1) subunit isoform was distributed primarily in spir al ligament and inner hair cells of the cochlea, and in crista ampulla ris and macula of the saccule. The beta(2) subunit isoform was most ab undant in the stria vascularis, dark cells of the ampullae and utricle . The alpha(1) beta(1) subunit combination of Na,K-ATPase was most com monly found in the spiral ligament, while the alpha(1) beta(2) combina tion was most abundant in the stria vascularis. Similarly, alpha(1) be ta(2) was confined more to the dark cells of the ampullae and utricle. The alpha(3) beta(1) subunit combination of Na,K-ATPase was identifie d in the inner hair cells of the cochlea and the sensory regions of th e vestibular end organs. These observations may reflect functional div ersity of Na,K-ATPase in the individual inner ear regions and may prov ide insight into the differences between fluid and ion transport in th e inner ear and that of other transporting tissues. Overall, the distr ibution pattern further indicates that the different isoform combinati ons have specific roles.