Resistance properties of the diluting segment of Amphiuma kidney: Influence of potassium adaptation

Hans Oberleithner, William Guggino, Gerhard Giebisch

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13 Scopus citations


Chronic exposure to high potassium stimulates K+-secretory mechanisms in the diluting segment of the amphibian kidney (K+ adaptation). Since K+ net flux depends critically on the passive cell membrane permeabilities for K+ ions, cable analysis and K+-concentration step changes were applied in this nephron segment to assess the individual resistances of the epithelium and the K+ conductance of the luminal cell membrane. Experiments were performed in the isolated, doubly-perfused kidney of both control and K+-adapted Amphiuma. In control animals transepithelial resistance was 290±27 Ωcm2, which decreased significantly to 199±17 Ωcm2 after K+ adaptation. The resistance in parallel of the luminal and peritubular cell membrane decreased from a control value of 157±14 to 108±6 Ωcm2 after chronic K+ treatment. This was paralleled by a decrease of the ratio of the luminal to peritubular cell membrane resistance from 2.5±0.1 to 1.9±0.1, respectively. Estimation of the individual cell membrane resistances reveals that the combined resistance of the luminal and peritubular cell membrane is in the same order of magnitude as the paracellular shunt resistance in diluting segments of both control and K+-adapted animals. The luminal cell membrane is K+ selective under both conditions, but the absolute luminal K+ conductance increases by some 60% with K+ adaptation. This leads to an increased back-leak of K+ from cell to lumen and may explain stimulated K+ net secretion found after chronic K+ loading.

Original languageEnglish (US)
Pages (from-to)139-147
Number of pages9
JournalThe Journal of Membrane Biology
Issue number2
StatePublished - Jun 1 1985
Externally publishedYes


  • K adaptation
  • K conductance
  • K transport
  • cable analysis
  • diluting segment

ASJC Scopus subject areas

  • Biophysics
  • Physiology
  • Cell Biology


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