title: Divalent cations regulate acidity within the lumen and tubulovesicle compartment of gastric parietal cells.
abstract: OBJECTIVE
  Until recently, it has not been possible to evaluate factors that regulate the acidity of the microenvironment within the tubulovesicles and luminal (TV/L) spaces of the gastric gland. The goal of this study was to develop a method for monitoring the mechanisms that regulate acidity in the TV/L compartment.
  
  
  METHODS
  Isolated rabbit gastric glands (intact or permeabilized with S. aureus alpha-toxin) were loaded with a recently characterized fluorescent dye, LysoSensor Yellow-Blue DND 160 (Molecular Probes, Eugene, OR), which localizes to highly acidic compartments and can be used to monitor acidity ratiometrically.
  
  
  RESULTS
  In resting glands, the pH of the TV/L compartment was approximately 3.4. Moderate alkalizations ( approximately 0.5 to 1.0 pH unit alkalization) were observed during exposure to inhibitors of the apical H(+)/K(+) ATPase (omeprazole and SCH28080), thereby unmasking a stable, low-level leak of H(+) ions from the TV/L compartment. Similar changes were observed in alpha-toxin permeabilized glands following depletion of ATP in the cytoplasm. In intact and permeabilized glands, we used the cell-permeant, divalent cation chelator, tetrakis-(2-pyridylmethyl)ethylenediamine (TPEN) to probe the effects of lowering divalent cation content of the TV/L compartment. Exposure to relatively low concentrations (20 micromol/L, 50 micromol/L) of TPEN reversibly promoted H(+) leakage. At these concentrations, simultaneous inhibition using SCH28080 led to marked enhancement of the rate of alkalization.
  
  
  CONCLUSIONS
  The effects of low-dose TPEN suggests that acidity within the TV/L compartment of the gastric gland may be regulated, at least in part, by its content of divalent cations such as Zn(2+), for which TPEN has high affinity.
authors.affiliation: Department of Surgery, Brigham and Women's Hospital, VA Boston Health Care System, Boston, MA 02115, USA.
authors.forename: Andrea
authors.initials: A
authors.lastname: Gerbino
authors.forename: Aldebaran M
authors.initials: AM
authors.lastname: Hofer
authors.forename: Breda
authors.initials: B
authors.lastname: McKay
authors.forename: Bonnie W
authors.initials: BW
authors.lastname: Lau
authors.forename: David I
authors.initials: DI
authors.lastname: Soybel
mesh_terms: D000818:Animals; D002413:Cations, Divalent / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002614:Chelating Agents / Q000494:pharmacology; D004533:Egtazic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005029:Ethylenediamines / Q000494:pharmacology; D005744:Gastric Acid / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007093:Imidazoles / Q000494:pharmacology; D066298:In Vitro Techniques; D009853:Omeprazole / Q000494:pharmacology; D010295:Parietal Cells, Gastric / Q000378:metabolism*; D054328:Proton Pump Inhibitors; D011817:Rabbits; D014018:Tissue Distribution
chemical_list: D002413:Cations, Divalent; D002614:Chelating Agents; D004791:Enzyme Inhibitors; D005029:Ethylenediamines; D007093:Imidazoles; D054328:Proton Pump Inhibitors; C035235:Sch 28080; C070379:1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid acetoxymethyl ester; D004533:Egtazic Acid; D009853:Omeprazole; C044387:N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine