Abstract
This study examined the presence of NaK-ATPase isoforms in the developing inner ear of the rat and studied the importance of functional subunit combinations in endolymph homeostasis. The findings were: (a) the combination α1β1 is found in epithelial, mesenchymal, and neural inner ear cells with an early starting expression 14 days postconception (dpc) in some endolymphatic sac cells; (b) from 1 day after birth (dab) expression of α1β2 is observed in marginal cells, vestibular dark cells, and certain vestibular nonsensory cells; (c) a transient expression of α2β1 is found in suprastrial fibrocytes and spiral ligament fibrocytes type II between 10 and 15 dab; (d) starting at 16 dpc the combination α3β1 is uniquely expressed in inner ear neural cells (as in other neural tissues). In conclusion, during development a switch from α2β1 towards α1β1 is observed in suprastrial fibrocytes and in spiral ligament fibrocytes type II. Thus, according to the biochemical characteristics of these combinations, a switch towards a NaK-ATPase with higher capacity takes place. In addition, prominent expression of the α1β2 combination in predominantly K+ ion transporting marginal and dark cells is in accordance with the characteristic of this combination and thus with the presumed function of these cells as important K+ suppliers for the endolymph. We believe this combination in certain vestibular nonsensory cells to be involved in K+ sensing. Early expression of the α1β1 combination in the endolymphatic sac, prior to that in the other parts of the inner ear, suggests that this structure may be involved to some extent in the development of the vestibulum and cochlea.
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Received: 1 August 2000 / Accepted: 30 October 2000
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Peters, T., Kuijpers, W. & Curfs, J. Occurrence of NaK-ATPase isoforms during rat inner ear development and functional implications. European Archives of Oto-Rhino-Laryngology 258, 67–73 (2001). https://doi.org/10.1007/s004050000304
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DOI: https://doi.org/10.1007/s004050000304