Mechanisms of HCl-induced lowering of intracellular pH in rabbit esophageal epithelial cells.
BACKGROUND
For acid injury to occur in esophageal epithelium, extracellular HCl must lower intracellular pH. Therefore, we sought to define the mechanisms for translation of low extracellular pH (pHo) into low intracellular pH (pHi).


METHODS
To define the mechanisms, primary cultures of rabbit esophageal epithelial cells were loaded with the pH-sensitive fluorescent dye, 2'7''-bis(carboxyethyl)-5(6)-carboxyfluorescein (BCECF), which enabled pHi to be recorded by microfluorimetry.


RESULTS
Lowering pHo to 6.0 with HCl caused pHi to decline at 0.07-0.08 units/min and produced an average cellular H+ load of 3-6 mmol/L at 1 minute and of 11 mmol/L at 5 minutes. This degree of acidification was primarily attributable to increased H+ entry via a 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS)-sensitive Clo-dependent mechanism because DIDS or exposure to Clo-free solution blocked cell acidification. Furthermore a contribution to low pHi at low pHo of abolition of acid extrusion via Na+/H+ and Na(+)-dependent Cl-/HCO3- exchangers was sought but not established because exposure at low pHo to either 5-(N-ethyl-N-isopropyl)amiloride (EIPA) or Na(+)-free solution + EIPA increased the degree of acid loading over untreated cells.


CONCLUSIONS
Low pHo results in low pHi in esophageal cells primarily because of increased H+ entry via a DIDS-sensitive, Clo-dependent mechanism consistent with the known acid-loading Na(+)-independent Cl-/HCO3- exchanger.
Tobey
N A
NA
Department of Medicine, Tulane University School of Medicine, New Orleans, Louisiana.
Reddy
S P
SP
Keku
T O
TO
Cragoe
E J
EJ
Orlando
R C
RC
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000584:Amiloride / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology; D017920:Antiporters / Q000502:physiology; D002478:Cells, Cultured; D027963:Chloride-Bicarbonate Antiporters; D003592:Cytophotometry; D004847:Epithelial Cells; D004848:Epithelium / Q000378:metabolism / Q000502:physiology; D004947:Esophagus / Q000166:cytology / Q000378:metabolism* / Q000502:physiology; D005452:Fluoresceins / Q000494:pharmacology; D006851:Hydrochloric Acid / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration / Q000187:drug effects*; D011817:Rabbits; D012964:Sodium / Q000502:physiology; D017923:Sodium-Hydrogen Exchangers / Q000502:physiology; D013997:Time Factors
D000889:Anti-Arrhythmia Agents; D017920:Antiporters; D027963:Chloride-Bicarbonate Antiporters; D005452:Fluoresceins; D017923:Sodium-Hydrogen Exchangers; D000584:Amiloride; C043829:2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein; D012964:Sodium; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D006851:Hydrochloric Acid; C039614:ethylisopropylamiloride