In situ measurement of pH in the secreting canaliculus of the gastric parietal cell and adjacent structures

Abstract

The gastric H(+)/K(+)-ATPase is located within an infolding (secretory canaliculus) of the apical plasma membrane of gastric parietal cells. Our aim was to measure the pH values in the cytosol and canaliculus of the acid-secreting parietal cell and the adjacent gland lumen in situ. We used ultrafine double-barreled tip-sealed microelectrodes at high acceleration rates for intracellular and canalicular measurements. Immunohistochemical staining of the parietal cells was used to identify the track of the electrode and to estimate the position of the electrode tip at the time of the last intracellular measurement. En route to the deepest regions of the mucosa, where the average gland lumen pH was approximately 3, and on advancing in steps of 2 mum, the electrode entered the cytosol of the parietal cells, where the pH value was 7.4. Advancing the electrode further resulted, in several instances, in a sharp decrease in pH to an average value of 1.7 +/- 0.2, which we interpreted as the measurement within the canaliculus. When the electrode was advanced even further, the pH reading returned to the cytosolic value. From the difference in pH between the secreting canaliculus and the adjacent gland lumen, we concluded that the released acid was immediately buffered. Thus, the only cellular structure directly exposed to the highly acidic canalicular content is the apical membrane forming the canaliculus in the parietal cell.

Helicobacter pylori colonization critically depends on postprandial gastric conditions

“…H. pylori has been shown to rely on a pH gradient across the mucus for spatial orientation25. In order to generate hypotheses why the luminal pH profile had such a strong effect on the numbers of H. pylori reaching the lower mucus layers, it was of interest to measure the pH within the mucus under these model conditions.…”

“…In order to generate hypotheses why the luminal pH profile had such a strong effect on the numbers of H. pylori reaching the lower mucus layers, it was of interest to measure the pH within the mucus under these model conditions. pH measurements within the mucus layer require the use of ultrafine double-barrelled microelectrodes, whose tips can be positioned to precisely defined locations within the mucus layer25. Due to technical obstacles, these measurements cannot be performed simultaneously with the in vivo experiments.…”

“…They also could not be performed with gerbil mucosa at all (see Methods for a technical explanation). In order to still be able to obtain measurements from within the mucus under the simulation conditions in the lumen, we used explanted gastric mucosa of the guinea pig, which is a highly standardized and well-documented model system for the study of gastric mucosal physiology25. We exposed four explanted guinea pig mucosae per profile to the same luminal pH changes as used for the in vivo experiments and measured the resulting pH values within the mucus at a depth of 20–40 µm below the luminal mucus surface.…”

CHAC1 overexpression in human gastric parietal cells with Helicobacter pylori infection in the secretory canaliculi

“…The present findings suggest that stable H. pylori colonization in the secretory canaliculi of parietal cells, rather than the presence of unstably attached H. pylori to foveolar epithelial cells, may be necessary to induce CHAC1 overexpression. The reason why H. pylori can live in the secretory canaliculus of the parietal cell, where the pH is extremely low, may be associated with H. pylori ‐mediated repression of the proton pump, the parietal cell enzyme mediating acid secretion, and ensuing hypochlorhydria in the secretory canaliculus of the infected parietal cell …”

A hydrogel based nanosensor with an unprecedented broad sensitivity range for pH measurements in cellular compartments

“…Furthermore, the canaliculus of gastric parietal cells functions as a storage of hydrochloric acid and it was reported that the pH of this compartment is about 1.7 measured by microelectrodes. 28 There are no reports to confirm these results by using optical pH nanosensors and the ratiometric measurement of low pH (<3) in living cells remains challenging.…”