Involvement of Calmodulin in the Inhibition of Na,K-ATPase by Ouabain

Lionel G. Leliévre, M. T. Piascik, J. D. Potter, E. T. Wallick, A. Schwartz

Research output: Contribution to journalArticlepeer-review

2 Scopus citations


This chapter discusses the involvement of calmodulin in the inhibition of Na,K-ATPase by ouabain. The sensitivity to ouabain of the membrane-bound Na,K-ATPase from murine plasmocytoma cells is altered by addition of Ca2+, plus membrane proteins or tropomyosin. Membranes treated with ethylenediaminetetraacetic acid (EDTA) (IC50 for ouabain Ca. 0.4–0.7 μM) recover the original resistance (IC50: 120 ± 20 μM). The Na,K-ATPase in the L fraction was half maximally inhibited by 1.5 ± 0.2 μM ouabain. After addition of tropomyosin (Tm) and Ca2+, the IC50 increased to 120 ± 20 μM. This shift was dependent upon the Tm and the free Ca2+ concentrations. At saturating (Ca2+), with 1 mg of L fraction, 330 pmoles Tm were required to shift 100% of ouabain-sensitive Na,K-ATPase form to the less sensitive form. To study the effect of free (Ca2+) on the alteration of sensitivity, the ratio of Tm to membrane protein is kept constant (330 pmole/mg). The chapter presents graphical representation of the dose-response curve of Na,K-ATPase activity versus ouabain concentration.

Original languageEnglish
Pages (from-to)1023-1027
Number of pages5
JournalCurrent Topics in Membranes and Transport
Issue numberC
StatePublished - Jan 1 1983

ASJC Scopus subject areas

  • Molecular Biology
  • Cell Biology


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