Cation flux in the ehrlich ascites tumor cell evidence for Na+-for-Na+ and K+-for-K+ exchange diffusion

Joseph T. Tupper

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Abstract

In a previous study, evidence was presented for an external Na+-dependent, ouabain-insensitive component of Na+ efflux and an external K+-dependent component of K+ efflux in the Ehrlich ascites tumor cell. Evidence is now presented that these components are inhibited by the diuretic furosemide and that under conditions of normal extracellular Na+ and K+ they represent Na+-for-Na+ and K-+for-K+ exchange mechanisms. Using 86Rb to monitor K+ movements, furosemide is shown to inhibit an ouabain-insensitive component of Rb+ influx and a component of Rb+ efflux, both representing approx. 30% of the total fux. Inhibition of Rb+ efflux is greatly reduced by removal of extracellular K+. Furosemide does not alter steady-state levels of intracellular K+ and it does not prevent cells depleted of K+ by incubation in the cold from regaining K+ upon warming. Using 22Na to monitor Na+ movements, furosemide is shown to inhibit an ouabain-insensitive component of unidirectional Na+ efflux which represents approx. 22% of total Na+ efflux. Furosemide does not alter steady-state levels of intracellular Na+ and does not prevent removal of intracellular Na+ upon warming from cells loaded with Na+ by preincubation in the cold. The ability of furosemide to affect unidirectional Na+ and K+ fluxes but not net fluxes is consistent with the conclusion that these components of cation movement across the cell membrane represent one-for-one exchange mechanisms. Data are also presented which demonstrate that the uptake of α-aminoisobutyrate is not affected by furosemide. This indicates that these components of cation flux are not directly involved in the Na+-dependent amino acid transport system A.

Original languageEnglish (US)
Pages (from-to)586-596
Number of pages11
JournalBiochimica et Biophysica Acta - Biomembranes
Volume394
Issue number4
DOIs
StatePublished - Jul 18 1975

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Ehrlich Tumor Carcinoma
Furosemide
Cations
Tumors
Cells
Fluxes
Ouabain
Amino Acid Transport System A
Cell membranes
Diuretics
Cell Membrane

ASJC Scopus subject areas

  • Biochemistry
  • Biophysics
  • Cell Biology
  • Medicine(all)

Cite this

Cation flux in the ehrlich ascites tumor cell evidence for Na+-for-Na+ and K+-for-K+ exchange diffusion. / Tupper, Joseph T.

In: Biochimica et Biophysica Acta - Biomembranes, Vol. 394, No. 4, 18.07.1975, p. 586-596.

Research output: Contribution to journalArticle

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