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Pflügers Archiv

, Volume 427, Issue 1–2, pp 143–150 | Cite as

An electrophysiological study of angiotensin II regulation of Na-HCO3 cotransport and K conductance in renal proximal tubules

I. Effect of picomolar concentrations
  • Salvatore Coppola
  • Eberhard Frömter
Transport Processes, Metabolism and Endocrinology; Kidney, Gastrointestinal Tract, and Exocrine Glands

Abstract

The effect of picomolar concentrations of angiotensin II (AII) was investigated in isolated perfused rabbit renal proximal tubules using conventional or pH-sensitive intracellular microelectrodes. Under control conditions cell membrane potential (Vb) and cell pH (pHi) averaged −53.8±1.9 mV (mean±SEM,n=49) and 7.24±0.01 (n=10), respectively. AII (at 10−11 mol/l), when applied from the bath (but not when applied from the lumen perfusate), produced the following effects: approximately 85% of the viable tubules responded with a small depolarization (+ 5.5±0.4 mV,n=43) which was accompanied in half of the pHi measurements by a slow acidification (ΔpHi=−0.03±0.01,n=5). The remaining 15% responded with a small hyperpolarization (ΔVb=−3.1±0.4 mV,n=6). All changes were fully reversible and repeatable. Experiments with fast changes in bath HCO3 or K concentrations, as well as measurements of the basolateral voltage divider fraction in response to transepithelial current flow, explain these observations as stimulation of a basolateral Na-HCO3 cotransporter and of a basolateral K conductance. Both counteract in their effect onVb, but can be individuated by blocker experiments with 4,4′-diisothiocyanatostilbene-2,2′-disulphonic acid (DIDS) and barium. Both the stimulation of Na-HCO3 cotransport and the stimulation of the K conductance may result from down-regulation of the level of cyclic adenosine monophosphate in the cell.

Key words

Rabbit renal proximal tubule Angiotensin II Cell potential Cell pH Na-HCO3 cotransport K conductance 

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Copyright information

© Springer-Verlag 1994

Authors and Affiliations

  • Salvatore Coppola
    • 1
  • Eberhard Frömter
    • 1
  1. 1.Zentrum der PhysiologieKlinikum der Johann Wolfgang Goethe-UniversitätFrankfurt/MainGermany

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