Regional distribution of Na,K-ATPase activity in porcine lens epithelium

Shigeo Tamiya, William L. Dean, Christopher A. Paterson, Nicholas A. Delamere

Research output: Contribution to journalArticle

43 Scopus citations

Abstract

PURPOSE. It has been established that Na,K-ATPase activity is higher in lens epithelium than fibers. However, others have suggested the Na,K-ATPase enzyme may be inactive or absent in the central 10% of the epithelium. Studies were conducted to measure and compare Na,K-ATPase specific activity and to examine Na,K-ATPase protein expression in the anterior and equatorial regions of porcine lens epithelium. METHODS. Na,K-ATPase activity was determined by measuring the ouabain-sensitive rate of adenosine triphosphate (ATP) hydrolysis. Western blot analysis was used to detect Na,K-ATPase catalytic subunit (α) and glycoprotein subunit (β) protein as well as β-actin which was used as a loading control. RESULTS. Na,K-ATPase specific activity was more than two times higher in the equatorial epithelium than the anterior 50% of the epithelium. However, the abundance of Na,K-ATPase α1 isoform protein was similar in the two regions. Neither the α2 nor α3 Na,K-ATPase isoform could be detected in the anterior or equatorial epithelium, but Na,K-ATPase β1 protein was detected in both regions. In contrast to the observed regional difference in Na,K-ATPase activity, the activity of a different P-type ATPase, plasma membrane Ca-ATPase (PMCA), was not significantly different in the anterior and central epithelium. Western blot analysis indicated the presence of two PMCA isoforms, PMCA2, and PMCA4. CONCLUSIONS. Na,K-ATPase activity is significantly higher at the equatorial region of the epithelium compared with the anterior, even though the level of Na,K-ATPase protein is similar in the two regions. It is possible that nonuniform distribution of functional Na,K-ATPase activity contributes to the driving force for circulating solute movement through the lens fiber mass.

Original languageEnglish (US)
Pages (from-to)4395-4399
Number of pages5
JournalInvestigative Ophthalmology and Visual Science
Volume44
Issue number10
DOIs
StatePublished - Oct 1 2003
Externally publishedYes

ASJC Scopus subject areas

  • Ophthalmology
  • Sensory Systems
  • Cellular and Molecular Neuroscience

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