Na(+)-dependent and -independent Cl-/HCO3- exchangers in cultured rabbit esophageal epithelial cells.
BACKGROUND
The mechanisms by which esophageal epithelial cells regulate intracellular pH (pHi) in a physiological solution are unknown.


METHODS
Basal-type esophageal cells growing in primary culture were loaded with the fluorescent dye 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein (BCECF) to study pHi by microfluorimetry.


RESULTS
The pHi in HEPES buffer was 7.7 +/- 0.03, a value higher than that in CO2/HCO3- buffer, 7.2 +/- 0.1. Cells in HEPES switched to CO2/HCO3- buffer rapidly acidified to pHi of 7, then alkalinized to a new steady-state pHi. The mechanisms for alkalinization in CO2/HCO3- were dependent on two exchangers, one amiloride-sensitive and the other 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS)-sensitive, the latter dependent on Nao and Cli, and so indicative of an Na(+)-dependent Cl-/HCO3- exchanger. Cells in a CO2/HCO3- buffer rapidly alkalinized to pH 8.2 when switched to HEPES, then acidified to a new steady-state pHi. Acidification in HEPES was largely caused by a DIDS-sensitive, Clo-dependent, non-Nao-requiring mechanism, indicative of a cell-acidifying Na-independent Cl-/HCO3- exchanger.


CONCLUSIONS
In a physiological buffer, esophageal cells have at least three exchangers for regulation of pHi.
Tobey
N A
NA
Department of Medicine, University of North Carolina School of Medicine, Chapel Hill.
Reddy
S P
SP
Khalbuss
W E
WE
Silvers
S M
SM
Cragoe
E J
EJ
Orlando
R C
RC
D000143:Acids / Q000378:metabolism; D000468:Alkalies / Q000378:metabolism; D000818:Animals; D001639:Bicarbonates / Q000494:pharmacology; D002021:Buffers; D002352:Carrier Proteins / Q000378:metabolism*; D002478:Cells, Cultured; D027963:Chloride-Bicarbonate Antiporters; D002772:Cholera Toxin / Q000494:pharmacology; D004847:Epithelial Cells; D004848:Epithelium / Q000378:metabolism; D004947:Esophagus / Q000166:cytology / Q000378:metabolism*; D006531:HEPES / Q000494:pharmacology; D006706:Homeostasis; D006863:Hydrogen-Ion Concentration; D007552:Isotonic Solutions / Q000494:pharmacology; D011817:Rabbits; D000077331:Ringer's Solution; D012964:Sodium / Q000494:pharmacology*
D000143:Acids; D000468:Alkalies; D001639:Bicarbonates; D002021:Buffers; D002352:Carrier Proteins; D027963:Chloride-Bicarbonate Antiporters; D007552:Isotonic Solutions; D000077331:Ringer's Solution; D002772:Cholera Toxin; D012964:Sodium; D006531:HEPES