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

First Author  Krick W Year  2009
Journal  Am J Physiol Renal Physiol Volume  297
Issue  1 Pages  F145-54
PubMed ID  19369292 Mgi Jnum  J:149840
Mgi Id  MGI:3849234 Doi  10.1152/ajprenal.90401.2008
Citation  Krick W, et al. (2009) Ability of sat-1 to transport sulfate, bicarbonate, or oxalate under physiological conditions. Am J Physiol Renal Physiol 297(1):F145-54
abstractText  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 muM, 53.8 +/- 10.9 muM, and 63.5 +/- 38.7 muM, respectively. Vice versa, [(14)C]oxalate uptake was inhibited by sulfate with a K(i) of 85.9 +/- 9.5 muM. 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.
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