Intracellular Na+, K+ and Cl- activities in Ehrlich ascites tumor cells

W. David Dawson, Thomas C. Smith

Research output: Contribution to journalArticlepeer-review

19 Scopus citations

Abstract

Ehrlich ascites tumor cell membrane potential (Vm) and intracellular Na+, K+ and Cl- activities were measured under steady-state conditions in normal saline medium (Na+ = 154, K+ = 6, Cl- = 150 mequiv./l). Membrane potential was estimated to be -23.3 ± 0.8 mV using glass microelectrodes. Intracellular ion activities were estimated with similar glass electrodes rendered ion-selective by incorporation of ion-specific ionophores. Measurements of Vm and ion-activity differences were made in the same populations of cells. Under these conditions the intracellular Na+, K+ and Cl- activities are 4.6 ± 0.5; 68.3 ± 8.0; and 43.6 ± 2.1 mequiv./l, respectively. The apparent activity coefficients for Na+ and K+ are 0.18 ± 0.02 and 0.41 ± 0.05 respectively. These are significantly lower than the activity coefficients expected for the ions in physiological salt solutions (0.71 and 0.73, respectively). The activity coefficient for intracellular Cl- (0.67 ± 0.03), however, is close to that of the medium (0.73), and the transmembrane electrochemical potential difference for Cl- is not different from zero. The results establish that the energy available from the Na+ electrochemical gradient is much greater than previously estimated from chemical measurements.

Original languageEnglish (US)
Pages (from-to)293-300
Number of pages8
JournalBBA - Biomembranes
Volume860
Issue number2
DOIs
StatePublished - Aug 21 1986
Externally publishedYes

Keywords

  • (Ehrlich ascites tumor cell)
  • Ion activity
  • Ion-selective electrode
  • Membrane potential

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Cell Biology

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