Ability of sat-1 to transport sulfate, bicarbonate, or oxalate under physiological conditions

Tubular reabsorption of sulfate is achieved by the sodium-dependent sulfate transporter, NaSi-1, located at the apical membrane, and the sulfate-anion exchanger, sat-1, located at the basolateral membrane. To delineate the physiological role of rat sat-1, [(35)S]sulfate and [(14)C]oxalate uptake int...

Full description

Saved in:
Bibliographic Details
Published in:American journal of physiology. Renal physiology 2009-07, Vol.297 (1), p.F145-F154
Main Authors: Krick, Wolfgang, Schnedler, Nina, Burckhardt, Gerhard, Burckhardt, Birgitta C
Format: Article
Language:English
Subjects:
Amino Acid Transport System A - genetics
Amino Acid Transport System A - metabolism
Animals
Bicarbonates - pharmacokinetics
Biological Transport - physiology
Cells
Female
Ion exchange
Ions
Kidneys
Membranes
Models, Biological
Oocytes - cytology
Oocytes - metabolism
Oxalates - pharmacokinetics
Patch-Clamp Techniques
Rats
Rodents
Salt
Sulfates - pharmacokinetics
Transfection
Xenopus laevis
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:Tubular reabsorption of sulfate is achieved by the sodium-dependent sulfate transporter, NaSi-1, located at the apical membrane, and the sulfate-anion exchanger, sat-1, located at the basolateral membrane. To delineate the physiological role of rat sat-1, [(35)S]sulfate and [(14)C]oxalate uptake into sat-1-expressing oocytes was determined under various experimental conditions. Influx of [(35)S]sulfate was inhibited by bicarbonate, thiosulfate, sulfite, and oxalate, but not by sulfamate and sulfide, in a competitive manner with K(i) values of 2.7 +/- 1.3 mM, 101.7 +/- 9.7 microM, 53.8 +/- 10.9 microM, and 63.5 +/- 38.7 microM, respectively. Vice versa, [(14)C]oxalate uptake was inhibited by sulfate with a K(i) of 85.9 +/- 9.5 microM. The competitive type of inhibition indicates that these compounds are most likely substrates of sat-1. Physiological plasma bicarbonate concentrations (25 mM) reduced sulfate and oxalate uptake by more than 75%. Simultaneous application of sulfate, bicarbonate, and oxalate abolished sulfate as well as oxalate uptake. These data and electrophysiological studies using a two-electrode voltage-clamp device provide evidence that sat-1 preferentially works as an electroneutral sulfate-bicarbonate or oxalate-bicarbonate exchanger. In kidney proximal tubule cells, sat-1 likely completes sulfate reabsorption from the ultrafiltrate across the basolateral membrane in exchange for bicarbonate. In hepatocytes, oxalate extrusion is most probably mediated either by an exchange for sulfate or bicarbonate.
ISSN:1931-857X
1522-1466
DOI:10.1152/ajprenal.90401.2008