Demonstration of a pH gradient in the gastric gland of the acid-secreting guinea pig mucosa

The gastric mucosa is covered by a continuous layer of mucus. Although important for understanding the mechanism of this protective function, only scarce information exists about the pH inside the gastric gland and its outlet. pH in the lumen of the gastric glands, in the outlet of gastric crypts, and in the adjacent cells was measured in the isolated acid-secreting mucosa of the guinea pig. Ultrafine double-barreled pH microelectrodes were advanced at high acceleration rates through the gastric mucus and the tissue to ensure precise intracellular and gland lumen pH measurements. A pH gradient was found to exist along the gastric gland, where the pH is 3.0 at parietal cells, i.e., in the deepest regions, and increases to 4.6 at the crypt outlet. Intracellular pH (pHi) of epithelial cells bordering a crypt outlet, and of neck cells bordering a gland, was acidic, averaging 6.0 and 6.5, respectively. pHi of deep cells bordering a gland was nearly neutral, averaging 7.1, and the secreting parietal cells were characterized by a slightly alkaline pHi of 7.5. This gland pH gradient is in general agreement with a model that we recently proposed for proton transport in the gastric mucus, in which protons secreted by the parietal cells are buffered to and transported with the simultaneously secreted mucus toward the gastric lumen, where they are liberated from the degraded mucus.

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Comparative Histological Study of the Stomach in Two Species of Iraqi Vertebrates (Magpie Pica pica L. and Small Asian Mongoose Herpestes javanicus E.)

Baghdad Science Journal ◽

10.21123/bsj.2019.16.2.0281 ◽

2019 ◽

Vol 16 (2) ◽

pp. 0281

Author(s):

AL –Nakeeb Et al.

Keyword(s):

Outer Layer ◽

Histological Study ◽

Gastric Gland ◽

Parietal Cells ◽

Pica Pica ◽

Gastric Glands ◽

Chief Cells ◽

Herpestes Javanicus ◽

Mucous Neck Cells ◽

Muscularis Externa

A histological study showed the wall of the stomach in Pica pica and Herpestes javanicus consists of four layers: mucosa, submucosa, muscularis externa and serosa. Also, the present study showed many differences in the histological structures of the stomach for each in both types. The stomach of P. pica consists of two portions: the proventiculus and gizzard, while the stomach of H. javanicus consists of three portions: cardiac, fundic and pyloric regions. The mucosa layer formed short gastric folds, named plicae. In the proventiculus of P. pica, sulcus is found between each two plicae, but the folds called gastric pits in the gizzard, which are full with koilin. Lamina properia in both types contained gastric glands (straight simple tubular glands) named superficial glands, as well as another gastric gland found in the submucosa layer of the proventiculus in P. pica only named deep gastric glands. The gastric gland in the stomach of H. javanicus contained: mucous neck cells and parietal cells positive to AB/PAS stains in cardiac portion, as well as chief cells in fundic portion, but pyloric portion had just mucous neck cells. Muscularis externa in both types formed two muscle layers: inner and outer layer.

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Gastrin stimulation of isolated gastric glands

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.1982.242.5.g504 ◽

1982 ◽

Vol 242 (5) ◽

pp. G504-G512 ◽

Cited By ~ 7

Author(s):

C. S. Chew ◽

S. J. Hersey

Keyword(s):

Time Course ◽

Gastric Gland ◽

Cell Activity ◽

Phosphodiesterase Inhibitor ◽

Parietal Cells ◽

Gastric Glands ◽

Histamine H2 Receptor ◽

Wide Range ◽

Isolated Cell ◽

Stimulation Of

The ability of gastrin to stimulate acid formation was studied in gastric glands and isolated parietal cells obtained from rabbit gastric mucosa. Accumulation of the weak base aminopyrine and increases in oxygen consumption were used as measures of acid secretory activity. The responses to gastrin were found to be very small (10-15% increase). However, inclusion of dithiothreitol (0.5 mM) in the incubation medium enhanced the responses in both glands and isolated cells to easily detectable levels. For the gastric gland preparation, gastrin stimulation was maximal at 1 X 10(-7) M, with an apparent ED50 of 5 nM. The response reached a maximum at about 30 min and was stable for at least an hour. The gastrin response was enhanced by the phosphodiesterase inhibitor isobutylmethylxanthine and partially inhibited by cimetidine, a histamine H2-receptor antagonist. Combinations of gastrin and histamine showed an additive response over a wide range of histamine concentrations. However, time-course studies revealed a transient potentiation of gastrin response by histamine, which reached a peak at 15 min and was reduced to an additive response by 30 min. Studies using isolated cell populations enriched in parietal cells (approximately 70%) revealed a gastrin stimulation that was not inhibited by cimetidine. The transient potentiation of the gastrin response by histamine was also found in the isolated cell preparation. Gastrin had no effect on cellular cAMP levels or adenylyl cyclase activity. The results are interpreted to indicate that gastrin stimulates acid secretion through three separate actions: 1) a direct stimulation of parietal cell activity, 2) a potentiating interaction with histamine, and 3) for more intact preparations, a release of histamine, which in turn acts as a paracrine stimulus. Quantitatively, the most important action appears to be the release of histamine. None of the actions of gastrin appear to involve a change in cAMP metabolism.

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Gastric mucus of the guinea pig: proton carrier and diffusion barrier

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.1997.272.1.g63 ◽

1997 ◽

Vol 272 (1) ◽

pp. G63-G70 ◽

Cited By ~ 21

Author(s):

S. Schreiber ◽

P. Scheid

Keyword(s):

Gastric Mucosa ◽

Guinea Pig ◽

Incubation Period ◽

Diffusion Barrier ◽

Proton Transport ◽

Gastric Epithelium ◽

Proton Release ◽

Gastric Mucus ◽

Gastric Lumen ◽

In Series

Proton transport with the gastric mucus was investigated in the guinea pig in vitro by use of three experimental series. In series I, pH profiles were obtained in the mucus and mucosa of a gastric explant with fine-tipped double-barreled microelectrodes. With a luminal pH of 1.8, pH increased across this layer to approximately 6 at the epithelial surface. Thickness of the gastric mucous gel layer increased continuously by 170 +/- 100 microns/h in the unstimulated and by 450 +/- 120 microns/h in the histamine-stimulated preparation (means +/- SD). In series II, fresh guinea pig gastric mucus was obtained from the gastric mucosa and titrated at 10 degrees C from pH 6.5 to 0.7, followed by an incubation period of 30 min at 37 degrees C. During this incubation period, a spontaneous acidic shift was observed, corresponding to a proton release from the mucus of 130 +/- 19 mM. This proton release could be blocked by the pepsin inhibitor pepstatin and was not observed when titrating down to only pH 3. Buffer values calculated as the mean slope of the titration curves in the pH range of 7 to 3 averaged 40 mM/pH unit. In series III, when titration was repeated with purified porcine mucin, no proton release was observed during incubation at pH 1.0, unless pepsinogen (375 U/ml) had been added before titration. Proton release during incubation at pH 1.0 and 37 degrees C in the presence of pepsinogen averaged 50 mM. The data suggest that protons secreted by the gastric mucosa are buffered by the continuously secreted mucus and transported, bound to the proteins of the mucus, toward the gastric lumen. During this transport, pepsinogen is converted within the mucus to pepsin. Pepsin modifies the buffering properties of the mucus, whereby protons are released from the protein binding. Thus the mucus forms a vehicle for proton transport toward the gastric lumen while, at the same time, constituting a diffusion barrier to prevent proton backdiffusion toward the gastric epithelium.

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Coupling of H(+)-K(+)-ATPase activity and glucose oxidation in gastric glands

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.1990.258.5.g719 ◽

1990 ◽

Vol 258 (5) ◽

pp. G719-G727 ◽

Cited By ~ 1

Author(s):

J. Fryklund ◽

K. Gedda ◽

D. Scott ◽

G. Sachs ◽

B. Wallmark

Keyword(s):

Atpase Activity ◽

Glucose Oxidation ◽

Gastric Gland ◽

Ph Gradient ◽

Co2 Production ◽

O2 Consumption ◽

Gastric Glands ◽

Major Mechanism ◽

Stimulation Of

The production of 14CO2 from uniformly labeled glucose was shown to account for the entire increase in histamine-stimulated O2 consumption in rabbit gastric glands when no other substrate was added to the medium. The increased production of CO2 was correlated to the increase in O2 consumption and the accumulation of [14C]-aminopyrine (AP) after stimulation with several secretagogues. Inhibitors of H(+)-K(+)-ATPase reduced the secretagogue-induced increase in CO2 production by greater than 90%, showing that the activity of this enzyme was responsible for the greater part of gastric gland metabolism under stimulated conditions. In contrast to AP accumulation, inhibition of CO2 production by omeprazole, an acid-activated inhibitor of the H(+)-K(+)-ATPase, was not reversed by washing. The reversal of AP accumulation after omeprazole treatment and washing was most likely due to a recruitment of residual pumps bordering a nonacidic space, which had not previously been inhibited by omeprazole. These residual pumps slowly generate a pH gradient and hence AP uptake. Adding NH4+ to gastric glands resulted in a concentration-dependent increase of CO2 production up to the maximal stimulated level but without formation of the pH gradient as measured by AP uptake and loss of the omeprazole inhibition of glucose oxidation. As NH4+ can act as a K+ surrogate for H(+)-K(+)-ATPase, and as NH3 is membrane permeant, full stimulation of CO2 production is evidence that the major mechanism of H(+)-K(+)-ATPase activation in situ is an increase in the KCl permeability of the pump membrane.

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Membrane-cytoskeleton dynamics in rat parietal cells: mobilization of actin and spectrin upon stimulation of gastric acid secretion.

The Journal of Cell Biology ◽

10.1083/jcb.108.2.441 ◽

1989 ◽

Vol 108 (2) ◽

pp. 441-453 ◽

Cited By ~ 62

Author(s):

F Mercier ◽

H Reggio ◽

G Devilliers ◽

D Bataille ◽

P Mangeat

Keyword(s):

Gastric Acid ◽

Dynamic Equilibrium ◽

Gastric Gland ◽

Cytoskeletal Proteins ◽

Parietal Cells ◽

Electron Microscopic Level ◽

Apical Surface ◽

Electron Microscopic ◽

Double Labeling ◽

Acid Secreting

The gastric parietal (oxyntic) cell is presented as a model for studying the dynamic assembly of the skeletal infrastructure of cell membranes. A monoclonal antibody directed to a 95-kD antigen of acid-secreting membranes of rat parietal cells was characterized as a tracer of the membrane movement occurring under physiological stimuli. The membrane rearrangement was followed by immunocytochemistry both at the light and electron microscopic level on semithin and thin frozen sections from resting and stimulated rat gastric mucosa. Double labeling experiments demonstrated that a specific and massive mobilization of actin, and to a lesser extent of spectrin (fodrin), was involved in this process. In the resting state, actin and spectrin were mostly localized beneath the membranes of all cells of the gastric gland, whereas the bulk of acid-secreting membranes appeared diffusely distributed in the cytoplasmic space of parietal cells without any apparent connection with cytoskeletal proteins. In stimulated cells, both acid-secreting material and actin (or spectrin) extensively colocalized at the secretory apical surface of parietal cells, reflecting that acid-secreting membranes were now exposed at the lumen of the secretory canaliculus and that this insertion was stabilized by cortical proteins. The data are compatible with a model depicting the membrane movement occurring in parietal cells as an apically oriented insertion of activated secretory membranes from an intracellular storage pool. The observed redistribution of actin and spectrin argues for a direct control by gastric acid secretagogues of the dynamic equilibrium existing between nonassembled (or preassembled) and assembled forms of cytoskeletal proteins.

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A physics-based model for maintenance of the pH gradient in the gastric mucus layer

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.00221.2017 ◽

2017 ◽

Vol 313 (6) ◽

pp. G599-G612 ◽

Cited By ~ 7

Author(s):

Owen L. Lewis ◽

James P. Keener ◽

Aaron L. Fogelson

Keyword(s):

Mucosal Surface ◽

Ph Gradient ◽

Model Parameters ◽

Regulation Mechanism ◽

Mucus Layer ◽

Gastric Mucus ◽

Epithelial Surface ◽

Ph Gradients ◽

Protective Function ◽

The Face

It is generally accepted that the gastric mucus layer provides a protective barrier between the lumen and the mucosa, shielding the mucosa from acid and digestive enzymes and preventing autodigestion of the stomach epithelium. However, the precise mechanisms that contribute to this protective function are still up for debate. In particular, it is not clear what physical processes are responsible for transporting hydrogen protons, secreted within the gastric pits, across the mucus layer to the lumen without acidifying the environment adjacent to the epithelium. One hypothesis is that hydrogen may be bound to the mucin polymers themselves as they are convected away from the mucosal surface and eventually degraded in the stomach lumen. It is also not clear what mechanisms prevent hydrogen from diffusing back toward the mucosal surface, thereby lowering the local pH. In this work we investigate a physics-based model of ion transport within the mucosal layer based on a Nernst-Planck-like equation. Analysis of this model shows that the mechanism of transporting protons bound to the mucus gel is capable of reproducing the trans-mucus pH gradients reported in the literature. Furthermore, when coupled with ion exchange at the epithelial surface, our analysis shows that bicarbonate secretion alone is capable of neutralizing the epithelial pH, even in the face of enormous diffusive gradients of hydrogen. Maintenance of the pH gradient is found to be robust to a wide array of perturbations in both physiological and phenomenological model parameters, suggesting a robust physiological control mechanism. NEW & NOTEWORTHY This work combines modeling techniques based on physical principles, as well as novel numerical simulations to test the plausibility of one hypothesized mechanism for proton transport across the gastric mucus layer. Results show that this mechanism is able to maintain the extreme pH gradient seen in in vivo experiments and suggests a highly robust regulation mechanism to maintain this gradient in the face of dynamic lumen composition.

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Fluorescence measurements of cytosolic free Na concentration, influx and efflux in gastric cells.

Cell Regulation ◽

10.1091/mbc.1.3.259 ◽

1990 ◽

Vol 1 (3) ◽

pp. 259-268 ◽

Cited By ~ 36

Author(s):

P A Negulescu ◽

A Harootunian ◽

R Y Tsien ◽

T E Machen

Keyword(s):

Cell Types ◽

Parietal Cells ◽

Acetoxymethyl Ester ◽

Gastric Glands ◽

Great Ability ◽

Chief Cells ◽

Fluorescence Measurements ◽

Na Efflux ◽

Rapid Perfusion ◽

Acid Secreting

Regulation of cytosolic free Na (Nai) was measured in isolated rabbit gastric glands with the use of a recently developed fluorescent indicator for sodium, SBFI. Intracellular loading of the indicator was achieved by incubation with an acetoxymethyl ester of the dye. Digital imaging of fluorescence was used to monitor Nai in both acid-secreting parietal cells and enzyme-secreting chief cells within intact glands. In situ calibration of Nai with ionophores indicated that SBFI fluorescence (345/385 nm excitation ratio) could resolve 2 mM changes in Nai and was relatively insensitive to changes in K or pH. Measurements on intact glands showed that basal Nai was 8.5 +/- 2.2 mM in parietal cells and 9.2 +/- 3 mM in chief cells. Estimates of Na influx and efflux were made by measuring rates of Nai change after inactivation or reactivation of the Na/K ATPase in a rapid perfusion system. Na/K ATPase inhibition resulting from the removal of extracellular K (Ko) caused Nai to increase at 3.2 +/- 1.5 mM/min and 3.5 +/- 2.7 mM/min in parietal and chief cells, respectively. Na buffering was found to be negligible. Addition of 5 mM Ko and removal of extracellular Na (Nao) caused Nai to decrease rapidly toward 0 mM Na. By subtracting passive Na efflux under these conditions (the rate at which Nai decreased in Na-free solution containing ouabain), an activation curve (dNai/Nai) for the Na/K ATPase was calculated. The pump demonstrated the greatest sensitivity between 5 and 20 mM Nai. At 37 degrees C the pump rate was less than 3 mM/min at 5 mM Nai and 26 mM/min at 25 mM Nai, indicating that the pump has a great ability to respond to changes in Nai in this range. Carbachol, which stimulates secretion from both cell types, was found to stimulate Na influx in both cell types, but did not have detectable effects on Na efflux. dbcAMP+IBMX, potent stimulants of acid secretion, had no effect on Na metabolism.

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VIP inhibits histamine-induced U1 trastructural changes related to acid secretion by parietal cells in isolated guinea pig gastric glands

Regulatory Peptides ◽

10.1016/0167-0115(83)90151-9 ◽

1983 ◽

Vol 6 (3) ◽

pp. 285 ◽

Cited By ~ 1

Author(s):

A. Anteunis ◽

C. Gespach ◽

A. Astesano ◽

S. Emami ◽

R. Robineaux ◽

...

Keyword(s):

Guinea Pig ◽

Acid Secretion ◽

Parietal Cells ◽

Gastric Glands

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Sonic hedgehog is associated with H+-K+-ATPase-containing membranes in gastric parietal cells and secreted with histamine stimulation

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.00389.2007 ◽

2008 ◽

Vol 295 (1) ◽

pp. G99-G111 ◽

Cited By ~ 24

Author(s):

Yana Zavros ◽

Melissa A. Orr ◽

Chang Xiao ◽

Danuta H. Malinowska

Keyword(s):

Sonic Hedgehog ◽

Proteolytic Enzymes ◽

Gradient Centrifugation ◽

Basolateral Membrane ◽

Gastric Gland ◽

Parietal Cells ◽

Human Gastric Cancer ◽

Gastric Glands ◽

Α Subunit ◽

Gastric Parietal Cells

Sonic hedgehog (Shh) is found within gastric parietal cells and processed from a 45-kDa to a 19-kDa bioactive protein by an acid- and protease-dependent mechanism. To investigate whether Shh is associated with the parietal cell membrane compartment that becomes exposed to both acid and proteolytic enzymes during acid secretion, the cellular location of Shh within resting and stimulated gastric parietal cells was examined. Immunofluorescence microscopy of rabbit stomach sections showed that Shh colocalized predominantly with parietal and pit, not chief/zymogen or neck, cell markers. In resting and histamine-stimulated rabbit gastric glands Shh was expressed only in parietal cells close to H+-K+-ATPase-containing tubulovesicular and secretory membranes with some colocalizing with γ-actin at the basolateral membrane. Gastric gland microsomal membranes were prepared by differential and sucrose gradient centrifugation and immunoisolation with an anti-H+-K+-ATPase-α subunit antibody. The 45- and 19-kDa Shh proteins were detected by immunoblot in immunopurified H+-K+-ATPase-containing membranes from resting and stimulated gastric glands, respectively. Incubating glands with a high KCl concentration removed Shh from the membranes. Histamine stimulated 19-kDa Shh secretion from gastric glands into the medium. In human gastric cancer 23132/87 cells cultured on permeable membranes, histamine increased 19-kDa Shh secretion into both apical and basolateral media. These findings show that Shh is a peripheral protein associated with resting and stimulated H+-K+-ATPase-expressing membranes. In addition, Shh appears to be expressed at or close to the basolateral membrane of parietal cells.

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