Cl(-)-HCO3- exchanger isoform AE2 is restricted to the basolateral surface of alveolar epithelial cell monolayers.
We investigated the polarized distribution and isoform specificity of anion exchange (Cl(-)-HCO3- exchange) in alveolar epithelial cell monolayers. Rat alveolar type II epithelial cell monolayers were grown in primary culture on detachable tissue culture-treated nuclepore filters. Each filter was mounted in a cuvette containing two fluid compartments (apical and basolateral) separated by the monolayer, the cells loaded with pH-sensitive dye, and intracellular pH (pHi) measured spectrofluorometrically. To assay for Cl(-)-HCO3- exchange, monolayers were incubated in medium containing 24 mM HCO3-/5% CO2 and 140 mM NaCl at pH 7.4 and acutely alkalinized by replacement of the fluid by HCO3(-)-free buffer containing Hepes (6 mM) at pH 7.4. Monolayers exhibited basolateral (but not apical) Cl(-)-dependent, Na(+)-independent recovery from an alkaline load that was abolished when Cl- was substituted by equimolar gluconate in the basolateral fluid, or if DIDS (500 microM) was present basolaterally. Substitution of gluconate for Cl- in the basolateral fluid, but not the apical fluid, resulted in a rise in steady-state pHi that was reversible on replacement of the basolateral fluid with Cl(-)-containing buffer, which occurred in HCO3(-)- but not Hepes-buffered medium. These data indicate that alveolar epithelial cells express basolateral membrane domain of these cells. Northern analysis of alveolar epithelial cell mRNA using anion exchanger (AE) isoform-specific cDNA probes indicates that alveolar epithelial cells express the AE2 isoform predominantly, if not exclusively, and do not express detectable AE1 (i.e., band-3 protein) or AE3.(ABSTRACT TRUNCATED AT 250 WORDS)
Lubman
R L
RL
Will Rogers Institute Pulmonary Research Center, Division of Pulmonary and Critical Care Medicine, University of Southern California, Los Angeles 90033.
Danto
S I
SI
Chao
D C
DC
Fricks
C E
CE
Crandall
E D
ED
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000818:Animals; D027321:Anion Transport Proteins; D017920:Antiporters / Q000235:genetics / Q000378:metabolism*; D001639:Bicarbonates / Q000378:metabolism*; D016764:Cell Polarity; D002478:Cells, Cultured; D027963:Chloride-Bicarbonate Antiporters; D002712:Chlorides / Q000378:metabolism*; D018076:DNA, Complementary; D004847:Epithelial Cells; D004848:Epithelium / Q000187:drug effects / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D011650:Pulmonary Alveoli / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D064606:SLC4A Proteins; D012964:Sodium / Q000378:metabolism
D027321:Anion Transport Proteins; D017920:Antiporters; D001639:Bicarbonates; D027963:Chloride-Bicarbonate Antiporters; D002712:Chlorides; D018076:DNA, Complementary; D008565:Membrane Proteins; D012333:RNA, Messenger; D064606:SLC4A Proteins; D012964:Sodium; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid