Na,K-ATPase activity decreases in the cochlear lateral wall of quiet-aged gerbils

M. A. Gratton, B. J. Smyth, B. A. Schulte, D. A. Vincent

Research output: Contribution to journalArticlepeer-review

12 Scopus citations


Alterations in the distribution and activity of Na,K-ATPase have been implicated in declining cell function with age. However, the location, size and anatomical complexity of the cochlea have limited study of this essential enzyme. Here we describe a micro-colorimetric assay which measures Na,K-ATPase activity in subregions of individual cochleae. Na,K-ATPase activity was determined in lateral wall and organ of Corti tissues by measuring liberation of inorganic phosphate (Pi) from ATP against a standard phosphate curve. Na,K-ATPase specific activity, expressed as μmol Pi liberated/mg protein/h, was calculted as the differences between total Pi liberated versus Pi liberated in the presence of ouabain. Na,K-ATPase specific activity and total protein content in the lateral wall significantly exceeded those of the organ of Corti. Although lateral wall protein content remained constant with age, Na,K-ATPase specific activity declined in some older gerbils, suggesting a basis for age-related reduction in magnitude of the endocochlear potential and confirming previous histochemical results. This microassay offers a sensitive, reliable means to assay enzyme activity in subregions or single turns of the cochlea that unlike other methods does not rely on use of radioisotopes, enzymatic cycling or sample pooling.

Original languageEnglish
Pages (from-to)43-50
Number of pages8
JournalHearing research
Issue number1-2
StatePublished - Mar 1995


  • Aging
  • Gerbil
  • Ion transport
  • Na,K-ATPase
  • Organ of Corti
  • Stria vascularis


Dive into the research topics of 'Na,K-ATPase activity decreases in the cochlear lateral wall of quiet-aged gerbils'. Together they form a unique fingerprint.

Cite this