Abstract
The mechanism of HCO −3 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 HCO −3 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 HCO −3 transport system exists across the peritubular cell membrane. (ii) This rheogenic peritubular Na+/HCO −3 cotransporter cooperates with a Na+/H+ exchanger in the luminal membrane, thus driving HCO −3 reabsorption. (iii) Reabsorption of HCO −3 and secretion of H+ depend upon the presence of carbonic anhydrase.
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Wang, W., Dietl, P. & Oberleithner, H. Evidence for Na+ dependent rheogenic HCO −3 transport in fused cells of frog distal tubules. Pflugers Arch. 408, 291–299 (1987). https://doi.org/10.1007/BF02181472
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DOI: https://doi.org/10.1007/BF02181472