Contribution of the Na+-K+-2Cl- cotransporter NKCC1 to Cl- secretion in rat OMCD

Am J Physiol Renal Physiol. 2001 May;280(5):F913-21. doi: 10.1152/ajprenal.2001.280.5.F913.


In rat kidney the "secretory" isoform of the Na+-K+-2Cl- cotransporter (NKCC1) localizes to the basolateral membrane of the alpha-intercalated cell. The purpose of this study was to determine whether rat outer medullary collecting duct (OMCD) secretes Cl- and whether transepithelial Cl- transport occurs, in part, through Cl- uptake across the basolateral membrane mediated by NKCC1 in series with Cl- efflux across the apical membrane. OMCD tubules from rats treated with deoxycorticosterone pivalate were perfused in vitro in symmetrical HCO/CO2-buffered solutions. Cl- secretion was observed in this segment, accompanied by a lumen positive transepithelial potential. Bumetanide (100 microM), when added to the bath, reduced Cl- secretion by 78%, although the lumen positive transepithelial potential and fluid flux were unchanged. Bumetanide-sensitive Cl- secretion was dependent on extracellular Na+ and either K+ or NH, consistent with the ion dependency of NKCC1-mediated Cl- transport. In conclusion, OMCD tubules from deoxycorticosterone pivalate-treated rats secrete Cl- into the luminal fluid through NKCC1-mediated Cl- uptake across the basolateral membrane in series with Cl- efflux across the apical membrane. The physiological role of NKCC1-mediated Cl- uptake remains to be determined. However, the role of NKCC1 in the process of fluid secretion could not be demonstrated.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • 4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / pharmacology
  • Algorithms
  • Animals
  • Bumetanide / pharmacology
  • Cells, Cultured
  • Chlorides / metabolism*
  • Diuretics / pharmacology
  • Hydrogen-Ion Concentration
  • Kidney Medulla / drug effects
  • Kidney Medulla / metabolism*
  • Kidney Tubules, Collecting / drug effects
  • Kidney Tubules, Collecting / metabolism*
  • Male
  • Rats
  • Rats, Sprague-Dawley


  • Chlorides
  • Diuretics
  • Bumetanide
  • 4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid