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Journal Article

Contraluminal bicarbonate transport in the proximal tubule of the rat kidney

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Ullrich,  Karl Julius
Department of Physiology, Max Planck Institute of Biophysics, Max Planck Society;

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Papavassiliou,  Friderun
Department of Physiology, Max Planck Institute of Biophysics, Max Planck Society;

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Citation

Ullrich, K. J., & Papavassiliou, F. (1987). Contraluminal bicarbonate transport in the proximal tubule of the rat kidney. Pflügers Archiv: European Journal of Physiology, 410(4-5), 501-504. doi:10.1007/BF00586532.


Cite as: http://hdl.handle.net/21.11116/0000-0008-1857-C
Abstract
In order to measure the contraluminal bicarbonate flux in situ we applied the stopped flow capillary microperfusion technique and measured the influx of 14C-bicarbonate buffer into cortical tubular cells at pH 8. It was found that the influx in percent of the starting concentration is larger at 20 mmol/l bicarbonate than at 1 mmol/l, indicating a sigmoidal type influx curve. At 20 mmol/l bicarbonate the influx was inhibited by 44%, when Na+ was replaced by choline. Replacement of gluconate by chloride or sulfate did not change H14CO3- influx. At this bicarbonate concentration, influx is inhibited by 10 mmol/l 4,4'-diisothiocyanato-2,2'-stilbenedisulfonate (DIDS) (22%), 5 mmol/l of the carbonic anhydrase blocker ethoxyzolamide (40%) as well as by 5 mmol/l of the arginine reagent 4-nitrophenylglyoxal (31%). At 1 mmol/l bicarbonate starting concentration, bicarbonate influx was inhibited when chloride in the perfusate was present or when sulphate was added. Replacement of sodium by choline did not change bicarbonate influx. Addition of DIDS and 8-anilino-naphthalene-1-sulfonate (5 mmol/l each) inhibited 1 mmol/l bicarbonate influx 39 and 49%, respectively. The para-amino-hippurate transport blocker dipropylsulfamoyl-benzoate (probenecid), the chloride channel blocker 5-nitro-2'-(3-phenylpropylamino)-benzoate (NPPB), the SH group blocker 2-(3-hydroxymercuri-2-methoxypropyl)-carbamoyl-phenoxyacetate (mersalyl), and formate did not inhibit bicarbonate influx, at 20 and at 1 mmol/l H14CO3- starting concentration.The data are compatible with the assumption of 1. a contraluminal (HCO3-)3/Na+ cotransporter inhibitable by DIDS, carbonic anhydrase inhibitors and 4-nitrophenylglyoxal, 2. a HCO3-/anion exchange system, which accepts sulfate and chloride and is inhibitable by the anion exchange blockers DIDS and 8-anilino-naphthalene-1-sulfonate, and 3. a HCO3- influx component which could not be influenced by Na+, Cl, nor by the inhibitors applied.