Validation of the use of the lipophilic thiocyanate anion for the determination of membrane potential in Ehrlich ascites tumor cells

Thomas C. Smith, Susan C. Robinson

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


The utility of the lipophilic anion thiocyanate (SCN+) as a probe for the indirect estimation of the cell membrane potential (Vm) in Ehrlich ascites tumor cells has been evaluated by comparison to direct electrophysiological measurements. SCN accumulation is consisten with first-order uptake into a single kinetically-identifiable cellular compartement, achieving steadystate distribution in 20-30 min at 22°C. The steady-state distribution ratio ([SCN-]c/[SCN-]e) in physiological saline is 0.44±0.02. Treatment of the cells with proparanolol (0.13 mM), an activator of Ca2+ dependent K+ channels, reduces the steady-state distribution ratio to 0.19±0.02. Conversely, treatmetn with BACl2 (10 mM), an antagonist of the pathway, increases the SCN- distribution ratio to 0.62±0.01. The equilibrium potentials (VSCN) calculated under these conditions are virtually identical to direct electrophysiological measurements of the Vm made under the same conditions. The effect of varing extracellular [K+]([K+]e) in the presence of constant [Na+]e=100 mM has also been tested. In control cells, elevation of [K+]e from 6 to 60 mM reduces VSCN from -20.6±1.0 to -13.2±1.2 mV. Again, microelectrode measurements give excellent quantitative agreement. Propranolol increases the sensitivity of the cells to varying [K+]e, so that a 10-fold elevation reduces VSCN by approximately 31 mV. BaCl2 greatly reduces this reponse: a 10-fold elevation in [K+]e yielding only a 4-mV rediction in VSCN. It is concluded that the membrane potential of Ehrlich cells can be estimated accurately from SCN- distribution measurements.

Original languageEnglish (US)
Pages (from-to)169-178
Number of pages10
JournalThe Journal of Membrane Biology
Issue number2
StatePublished - Feb 1989
Externally publishedYes


  • barium
  • Ehrlich ascites tumor cell
  • K channels
  • lipophilic anions
  • membrane potential
  • propranlol
  • thiocyanate

ASJC Scopus subject areas

  • Biophysics
  • Physiology
  • Cell Biology


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