title: Na(+)-dependent sulfate transport in opossum kidney cells is DIDS sensitive.
abstract: Sulfate transport was examined in OK/E cells, a clonal subline of opossum kidney cells that express several differentiated functions of the proximal tubule. Extracellular Na+ stimulated [35S]sulfate uptake five- to sixfold. Hill analysis demonstrating the dependence of sulfate uptake on Na+ concentration yielded a Hill coefficient of 1.5 and a Michaelis constant (KNa+) of 23 mM. Na(+)-dependent sulfate uptake was increased by lowering the pH from 7.4 to 6.4, decreased by raising the pH to 8.4 and inhibited by a 10-fold molar excess of SO3(2-), S2O3(2-) and CrO4(2-), but not by phosphate. The Na(+)-mediated component of sulfate uptake was saturable and kinetic parameters were estimated [Michaelis constant (Km) = 2.4 +/- 0.2 mM and maximum velocity (Vmax) = 125 +/- 15 pmol.mg protein-1.min-1]. Omitting extracellular Cl- resulted in a significant increase in the affinity of the carrier for sulfate (Km = 0.5 mm), without changing Vmax, consistent with competitive inhibition by Cl-. Na(+)-dependent sulfate uptake in OK/E cells was also inhibited by HCO3- [half-maximal inhibitory concentration (IC50) = 7 mM], 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS, IC50 = 0.9 microM), 0.5 mM picrylsulfonic acid and 0.1 mM ethacrynic acid, but not by 1 mM amiloride. Na(+)-dependent, DIDS-sensitive sulfate uptake was also expressed in the parental OK cell line and was not influenced by serum or 3,3',5-triiodo-L-thyronine. We conclude that Na(+)-dependent sulfate uptake in OK/E cells observes many of the features of Na(+)-sulfate cotransport in the renal brush-border membrane and provides a useful model to investigate the regulation of renal sulfate transport.
authors.affiliation: Department of Pediatrics, McGill University, Montreal, Quebec, Canada.
authors.forename: H S
authors.initials: HS
authors.lastname: Tenenhouse
authors.forename: J
authors.initials: J
authors.lastname: Martel
mesh_terms: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002460:Cell Line; D007668:Kidney / Q000166:cytology / Q000378:metabolism*; D051379:Mice; D008871:Microvilli / Q000378:metabolism; D009893:Opossums; D012964:Sodium / Q000494:pharmacology*; D013431:Sulfates / Q000493:pharmacokinetics*
chemical_list: D013431:Sulfates; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; D012964:Sodium; D000469:Alkaline Phosphatase; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid