Distribution of Immunoreactive Alpha- and Beta-subunit Isoforms of Na,K-ATPase in the Gerbil Inner Ear

Biochemical and histochemical studies have demonstrated abundant Na,K-ATPase in the inner ear and provided new information concerning the ion transport capacities of specialized cell types. To extend these earlier observations, we immunostained inner ears from adult gerbils with antibodies specific for the three known alpha- and the two known beta-isoforms of Na,K-ATPase. Different inner ear cell types contained specific and distinct combinations of alpha- and beta-subunit isoforms. Strial marginal cells and vestibular dark cells expressed the alpha 1- and beta 2-isoforms, whereas other positive epithelial cells expressed alpha 1 in combination with beta 1. Ganglion neurons and their peripheral processes showed positive immunostaining for the alpha 3- and beta 1-subunit isoforms. Subpopulations of fibrocytes in the spiral prominence, suprastrial and supralimbal regions, and vestibular system expressed either the alpha 1- or alpha 2-isoform, or both. The differential expression of Na,K-ATPase subunit isoforms presumably reflects different K+ and Na+ transport capacities among inner ear cell types which, working in concert, serve to generate and maintain the unique ionic and electrical environment in the mammalian inner ear.