Immunolocalization of Na+, K+-ATPase, Ca++-ATPase, Calcium-Binding Proteins, and Carbonic Anhydrase in the Guinea Pig Inner Ear

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Abstract
The distribution of Na+, K+-ATPase, Ca++-ATPase, carbonic anhydrase, and calcium-binding proteins were investigated immunohistochemically in paraffin sections of guinea pig inner ears. Marginal cells of the stria vascularis, type II fibrocytes of the spiral ligament, and cells in supralimbal and suprastrial regions, were positive for Na+, K+-ATPase. Type I fibrocytes of the spiral ligament were positive for Ca++-ATPase, carbonic anhydrase, calmodulin and osteopontin. In the vestibular system, dark cells were positive for Na+, K+ -ATPase. However, these cells and subepithelial fibrocytes were negative for Ca++-ATPase, carbonic anhydrase, and the calcium-binding proteins. In the endolymphatic sac, epithelial cells in intermediate and distal portions were positive for Na+, K+-ATPase, but the reaction was less than that in the stria. The same endolymphatic sac cells that were positive for Na+, K+-ATPase were also positive for Ca++-ATPase and calcium-binding proteins, but negative for carbonic anhydrase. The presence of Ca++-ATPase and calcium-binding proteins in the type I fibrocytes of the spiral ligament suggests that these cells are involved in mediating Ca++ regulation. Lower levels of Na+, K+-ATPase and the co-existence of Ca++-ATPase and calcium-binding proteins in the epithelial cells of the endolymphatic sac indicate that these cells have a distinctive role in ion transport that is different from that of the cells of the stria vascularis and vestibular dark cells.