Cellular mechanisms of Cl- transport in outer medullary collecting duct.
The OMCDi secretes Cl- when perfused and bathed with symmetrical solutions. The route for this transepithelial Cl- movement appears to be the paracellular pathway, and the driving force is the lumen positive voltage generated by the process of electrogenic H+ secretion. Currently, there is no evidence to support the existence of a significant transcellular route for transepithelial Cl- movement. Although the primary function of the OMCDi is related to urine acidification, Cl- plays an important role in this process. The basolateral membrane of the OMCDi cell contains a band-3 related Cl-/HCO3- antiporter and a Cl- conductance. The Cl-/HCO3- antiporter serves as the primary route for the efflux of HCO3- generated during the process of H+ secretion. The Cl- conductance allows Cl- brought into the cell by the antiporter to recycle across this membrane. This conductance also serves to maintain cell charge balance. Accordingly, for each equivalent of H+ leaving the cell across the apical membrane, a Cl- equivalent exits the cell across the basolateral membrane. Based on whole-cell patch-clamp studies, this Cl- conductance is blocked by the Cl- channel blocker DPC. This conductance may also have a finite permeability to HCO3-, and thus could serve as a secondary route for cellular HCO3- efflux. Lastly, the conductance is activated by the beta-adrenergic agonist isoproterenol.
Koeppen
B
B
Division of Nephrology, University of Connecticut Health Center, Farmington.
Pappas
C
C
Manger
T
T
Oyler
A
A
D000818:Animals; D001692:Biological Transport; D002352:Carrier Proteins / Q000378:metabolism; D027963:Chloride-Bicarbonate Antiporters; D002712:Chlorides / Q000378:metabolism*; D007679:Kidney Medulla; D007685:Kidney Tubules, Collecting / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism
D002352:Carrier Proteins; D027963:Chloride-Bicarbonate Antiporters; D002712:Chlorides; D008565:Membrane Proteins