Demonstration of a functional apical sodium hydrogen exchanger in isolated rat gastric glands

Abstract

Previous studies have shown that gastric glands express at least sodium-hydrogen exchanger (NHE) isoforms 1-4. Our aim was to study NHE-3 localization in rat parietal cells and to investigate the functional activity of an apical membrane NHE-3 isoform in parietal cells of rats. Western blot analysis and immunohistochemistry showed expression of NHE-3 in rat stomach colocalizing the protein in parietal cells together with the β-subunit of the H+-K+-ATPase. Functional studies in luminally perfused gastric glands demonstrated the presence of an apical NHE isoform sensitive to low concentrations of 5-ethylisopropyl amiloride (EIPA). Intracellular pH measurements in parietal cells conducted in omeprazole-pretreated superfused gastric glands showed an Na+-dependent proton extrusion pathway that was inhibited both by low concentrations of EIPA and by the NHE-3 specific inhibitor S3226. This pathway for proton extrusion had a higher activity in resting glands and was inhibited on stimulation of histamine-induced H+-K+-ATPase proton extrusion. We conclude that the NHE-3 isoform located on the apical membrane of parietal cells offers an additional pathway for proton secretion under resting conditions. Furthermore, the gastric NHE-3 appears to work under resting conditions and inactivates during periods of H+-K+-ATPase activity.

Effect of NSAIDs on Na+/H+ exchanger activity in rat colonic crypts

“…For example, the role of NHE isoforms 1-4 in pH balance was investigated on parietal cells of stomach tissue (25). By preferentially inhibiting NHE-3 activity using low-dose EIPA, researchers demonstrated that Na ϩ /H ϩ exchange isoforms offered an alternative pathway for H ϩ ion removal from the apical surface of the parietal glands (25).…”

Trefoil Factor 2 Requires Na/H Exchanger 2 Activity to Enhance Mouse Gastric Epithelial Repair

“…It is clear that the forward mode of heterologously expressed NHE2 Na/H exchange is fully inhibited when extracellular pH is below pH 6 (41). Elegant experiments have shown that the apical NHE3 present in rat parietal cells inactivates when acid secretion is ongoing (17) but that the basolateral NHE in guinea pig surface cells is active at luminal pH 1.5-5 (18). Although NHE2 activation by either damage or TFF remains unproven, in this scenario, it could produce an advantageous raising of surface pH to promote epithelial repair with cells exposed to a less stressful pH environment (as long as the resultant cellular acid load could be handled by buffers or basolateral transporters).…”

The calcium-sensing receptor acts as a modulator of gastric acid secretion in freshly isolated human gastric glands

“…Tissue was then transferred to the stage of a dissecting microscope and sliced into 0.5-cm square sections. Individual glands were isolated using a hand dissection technique as described previously (8,13) at a temperature of about 10°C. After isolation, the glands were transferred to coverslips precoated with adhesive Cell-Tak (BD Cell-Tak Cell and Tissue Adhesion, BD Biosciences) and mounted in a thermostatically controlled chamber maintained at 37°C on an inverted microscope (Zeiss Axiovert 200) equipped with an video-imaging system for the duration of the experiment.…”

“…Human stomach samples were washed several times with PBS and fixed by immersion with paraformaldehydelysine-periodate fixative (16) overnight at 4°C. Stomachs were washed three times with PBS, and thin sections were cut at a thickness of 5 m after cryoprotection with 2.3 M sucrose in PBS for at least 12 h. Immunostaining was carried out as described previously (13). Sections were incubated with 1% SDS for 5 min, washed three times with PBS, and incubated with PBS containing 1% BSA for 15 min before incubation with the primary antibody.…”