The influence of thapsigargin on na,k-ATPase activity in cultured nonpigmented ciliary epithelial cells

Takezo Mito, Soichiro Kuwahara, Nicholas A. Delamere

Research output: Contribution to journalArticle

4 Scopus citations

Abstract

Experiments were conducted to test the influence of thapsigargin on the Na,K-ATPase activity of cultured cells (ODM2) derived from human nonpigmented ciliary epithelium. The rate of ouabain-sensitive ATP hydrolysis (Na,K-ATPase activity) was diminished in cells that had been pretreated with thapsigargin then permeabilized. Following 20 min exposure of intact cells to thapsigargin, the cells were permeabilized with digitonin and the rate of ouabain-sensitive ATP hydrolysis (Na,K-ATPase activity) was measured immediately in a calcium-free buffer. In permeabilized cells that had been pretreated with 1 μM thapsigargin for 20 min, the rate of ouabain-sensitive ATP hydrolysis (Na,K-ATPase activity) was reduced by 38%. Pretreatment with lesser concentrations of thapsigargin caused smaller changes of Na,K-ATPase activity. The decrease of Na,K-ATPase activity was the same whether or not calmodulin antagonists W7 or trifluoperazine were present during the thapsigargin pretreatment period. This inhibitory effect upon the Na,K-ATPase may serve to limit the extent of sodium pump activation that takes place in intact cells when thapsigargin causes sodium pump stimulation by a mechanism that appears to involve changes in cytoplasmic ion levels when potassium channels open.

Original languageEnglish (US)
Pages (from-to)651-657
Number of pages7
JournalCurrent Eye Research
Volume14
Issue number8
DOIs
StatePublished - Jan 1 1995
Externally publishedYes

Keywords

  • ATP hydrolysis
  • Human ciliary epithelium
  • Na,K-ATPase
  • Thapsigargin

ASJC Scopus subject areas

  • Ophthalmology
  • Sensory Systems
  • Cellular and Molecular Neuroscience

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