title: An electrophysiological study of angiotensin II regulation of Na-HCO3 cotransport and K conductance in renal proximal tubules. I. Effect of picomolar concentrations.
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 (delta pHi = -0.03 +/- 0.01, n = 5). The remaining 15% responded with a small hyperpolarization (delta Vb = -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 on Vb, 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.
authors.affiliation: Zentrum der Physiologie, Klinikum der Johann Wolfgang Goethe-Universität, Frankfurt/Main, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Coppola
authors.forename: E
authors.initials: E
authors.lastname: Frömter
mesh_terms: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D001464:Barium / Q000494:pharmacology; D002352:Carrier Proteins / Q000378:metabolism*; D004553:Electric Conductivity; D004594:Electrophysiology; D005260:Female; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007687:Kidney Tubules, Proximal / Q000187:drug effects* / Q000378:metabolism*; D008839:Microelectrodes; D009994:Osmolar Concentration; D011188:Potassium / Q000502:physiology*; D011817:Rabbits; D027982:Sodium-Bicarbonate Symporters
chemical_list: D002352:Carrier Proteins; D027982:Sodium-Bicarbonate Symporters; D000804:Angiotensin II; D001464:Barium; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D011188:Potassium