Evidence for Na+ dependent rheogenic HCO3- transport in fused cells of frog distal tubules

W. Wang, P. Dietl, H. Oberleithner

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The mechanism of HCO3- transport was studied applying microelectrodes in "giant" cells fused from single epithelial cells of the diluting segment of frog kidney. A sudeen increase of extracellular HCO3- concentration from 10 to 20 mmol/l at constant pH hyperpolarized the cell membrane potential of the fused cell. This cell-voltage response was totally abolished by 10-3 mol/l SITS and significantly reduced by 10-4 mol/l acetazolamide or by omission of Na+ from the extracellular perfusate. Removal of Na+ from the perfusate caused a transient depolarization. Reapplication of Na+ induced a transient hyperpolarization. 10-3 mol/l SITS abolished the cell-voltage response to removal and reapplication of Na+. In the intact diluting segment of the isolated perfused frog kidney peritubular perfusion of 10-4 mol/l acetazolamide reduced the limiting transepithelial electrochemical gradient for H+ significantly from 30±4 mV to 14±3 mV. The results suggest: (i) In the diluting segment of the frog kidney a Na+-dependent rheogenic HCO3- transport system exists across the peritubular cell membrane. (ii) This rheogenic peritubular Na+/HCO3- cotransporter cooperates with a Na+/H+ exchanger in the luminal membrane, thus driving HCO3- reabsorption. (iii) Reabsorption of HCO3- and secretion of H+ depend upon the presence of carbonic anhydrase.

Original languageEnglish
Pages (from-to)291-299
Number of pages9
JournalPflugers Archiv European Journal of Physiology
Issue number3
StatePublished - Mar 1987
Externally publishedYes


  • Acetazolamide
  • Cell fusion
  • Cotransport
  • Diluting segment
  • Frog kidney
  • Na/HCO
  • SITS


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