title: Effect of CO2 on pHi in rabbit parietal, chief, and surface cells.
abstract: We investigated the pH recovery mechanisms in rabbit parietal, chief, and surface cells during pH shifts induced by introduction or removal of exogenous CO2-HCO3-. Intracellular pH (pHi) was measured using the fluorescent dye 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescin (BCECF). Gastric cells were highly purified by density gradient centrifugation and elutriation. When cells suspended in N-2-hydroxyethylpiperazene-N'-2-ethanesulfonic acid (HEPES)-100% O2, extracellular pH (pHo) 7.4, were exposed to 24 mM HCO3- -5% CO2, pHo 7.4, all cells quickly acidified by 0.3-0.4 pH units. Almost complete pH-recovery occurred within 15 min. In parietal cells, 70% of this recovery was dependent on the presence of extracellular Na+ (Nao+) and was blocked by 1 mM amiloride. The Na+-independent recovery was blocked by intracellular Cl- depletion or by 0.4 mM 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS). In chief cells and surface cells no recovery occurred in the absence of NaO+, and 1 mM amiloride blocked pH recovery in Na+-containing buffer. On removal of HCO3- -CO2, the cells alkalinized, and subsequent pH recovery was fast, substantially extracellular Cl- (ClO-) and DIDS inhibitable in parietal cells but slow and ClO- -independent in chief and surface cells. These results suggest that during intracellular acidification the Na+-H+ exchanger is the major pH regulator in these three gastric cell types even in the presence of HCO3-. During alkalinization the Cl- -HCO3-(OH-) exchanger is the predominant pH recovery mechanism in parietal, but not in chief and surface cells. In parietal cells, this exchanger is also involved in recovery from acidification.
authors.affiliation: Department of Surgery, Beth Israel Hospital, Boston, Massachusetts 02215.
authors.forename: U
authors.initials: U
authors.lastname: Seidler
authors.forename: K
authors.initials: K
authors.lastname: Carter
authors.forename: S
authors.initials: S
authors.lastname: Ito
authors.forename: W
authors.initials: W
authors.lastname: Silen
mesh_terms: D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D002245:Carbon Dioxide / Q000494:pharmacology*; D002712:Chlorides / Q000494:pharmacology; D005744:Gastric Acid / Q000378:metabolism*; D005753:Gastric Mucosa / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D010295:Parietal Cells, Gastric / Q000187:drug effects / Q000502:physiology*; D011817:Rabbits; D012016:Reference Values; D012964:Sodium / Q000494:pharmacology
chemical_list: D002712:Chlorides; D002245:Carbon Dioxide; D000584:Amiloride; D012964:Sodium