Characterization of basolateral chloride/bicarbonate exchange in macula densa cells.
Functional and immunohistological studies were performed to identify basolateral chloride/bicarbonate exchange in macula densa cells. Using the isolated, perfused thick ascending limb with attached glomerulus preparation dissected from rabbit kidney, macula densa intracellular pH (pH(i)) was measured with fluorescence microscopy and BCECF. For these experiments, basolateral chloride was reduced, resulting in reversible macula densa cell alkalinization. Anion exchange activity was assessed by measuring the maximal net base efflux on readdition of bath chloride. Anion exchange activity required the presence of bicarbonate, was independent of changes in membrane potential, did not require the presence of sodium, and was inhibited by high concentrations of DIDS. Inhibition of macula densa anion exchange activity by basolateral DIDS increased luminal NaCl concentration-induced elevations in pH(i). Immunohistochemical studies using antibodies against AE2 demonstrated expression of AE2 along the basolateral membrane of macula densa cells of rabbit kidney. These results suggest that macula densa cells functionally and immunologically express a chloride/bicarbonate exchanger at the basolateral membrane. This transporter likely participates in the regulation of pH(i) and might be involved in macula densa signaling.
Department of Medicine, Division of Nephrology, University of Alabama at Birmingham, Birmingham, Alabama, USA. pkomlosi@uab.edu
Peter
P
Komlosi
Sebastian
S
Frische
Amanda L
AL
Fuson
Attila
A
Fintha
Akos
A
Zsembery
Janos
J
Peti-Peterdi
P Darwin
PD
Bell
D000136:Acid-Base Equilibrium / Q000502:physiology*; D000818:Animals; D027321:Anion Transport Proteins / Q000494:pharmacology*; D000906:Antibodies; D017920:Antiporters / Q000494:pharmacology*; D027963:Chloride-Bicarbonate Antiporters / Q000502:physiology*; D006863:Hydrogen-Ion Concentration; D007150:Immunohistochemistry; D008564:Membrane Potentials; D009399:Nephrons / Q000166:cytology / Q000276:immunology / Q000502:physiology*; D011817:Rabbits; D064606:SLC4A Proteins; D015398:Signal Transduction; D012964:Sodium / Q000493:pharmacokinetics
D027321:Anion Transport Proteins; D000906:Antibodies; D017920:Antiporters; D027963:Chloride-Bicarbonate Antiporters; D064606:SLC4A Proteins; D012964:Sodium