Regulation of intracellular pH in isolated Necturus gastric mucosa during short-term exposure to luminal acid.
OBJECTIVE
Continuous exposure to gastric acid implies efficient control mechanisms of intracellular pH (pHi) in the gastric epithelium. This study assessed the roles of Na+, H+, and HCO3- transport mechanisms in controlling pHi during short-term exposure of the gastric epithelium to luminal acid.


METHODS
pHi and Na+ activity (aiNa) were measured with liquid sensor microelectrodes in isolated Necturus antral mucosa, modulating ion transport mechanisms by ion removal and pharmacological inhibition.


RESULTS
Short-term exposure to luminal acid (pH 2.3) acidified pHi by 0.3 pH units, whereafter pHi stabilized. This was associated with transient increase in aiNa. Blocking of Na+/H+ exchange (in the presence of HCO3-/CO2) by removal of Na+ or addition of amiloride eliminated the increase in aiNa and resulted in uncontrolled acidification of pHi. Similarly, blocking of HCO3- transport (in the presence of Na+) by removal of HCO3-/CO2 or addition of 4-acetamido-4-isothiocyanatostilbene-2,2-disulfonic acid resulted in uncontrolled acidification of pHi despite increase in aiNa. Blocking of Na+/K+ exchange with ouabain eliminated the recovery of aiNa and also resulted in uncontrolled acidification of pHi.


CONCLUSIONS
The data indicate that during short-term exposure of the gastric mucosa to luminal acid, both Na+/H+ antiport and HCO3- transport are needed to control pHi and maintain it within physiological ranges.
Kiviluoto
T
T
Second Department of Surgery, Helsinki University Central Hospital, Finland.
Mustonen
H
H
Salo
J
J
Kivilaakso
E
E
D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000494:pharmacology; D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D001692:Biological Transport; D005753:Gastric Mucosa / Q000187:drug effects / Q000378:metabolism*; D006851:Hydrochloric Acid / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration; D007552:Isotonic Solutions / Q000378:metabolism; D009338:Necturus maculosus; D010042:Ouabain / Q000494:pharmacology; D000077331:Ringer's Solution; D013997:Time Factors
D007552:Isotonic Solutions; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; D010042:Ouabain; D000584:Amiloride; D000077331:Ringer's Solution; D006851:Hydrochloric Acid