Circadian ultrastructural changes in rat gastric parietal cells under altered feeding regimens: A morphometric study

The fluorescent Ca2+ indicator fura 2 was used to measure cytosolic free [Ca2+] ([Ca2+]i) in order to obtain information about relative rates of Ca2+ influx into parietal cells during treatment with carbachol (a cholinergic agonist) or thapsigargin (TG, a Ca(2+)-mobilizing agent) or during reloading of the internal Ca2+ stores. In Ca(2+)-containing solutions, carbachol-, TG-, and reloading-stimulated Ca2+ entry exhibited nearly identical sensitivity to La3+ [inhibition constant (Ki) approximately 10 microM] or low pH (pKi approximately 7.0). In experiments in which carbachol and TG were used, there was no additional increase in [Ca2+]i when TG was added to carbachol-treated cells or when carbachol was added to cells previously treated with TG. Thus it is likely that a single Ca2+ entry pathway serves a signaling function as well as a role in refilling the Ca2+ store during reloading. Because the Ca2+ pathway is exquisitely sensitive to pH and serosal pH increases during stimulant-induced H+ secretion (which is activated by increases in [Ca2+]i), this mechanism will exert positive feedback on parietal cells in the intact stomach. When parietal cells were pretreated with carbachol in Ca(2+)-free solutions, reloading was independent of pH and La3+, suggesting that Ca(2+)-containing solutions should be used to determine the properties of the influx pathway.

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Receptor-operated Ca2+ channels in gastric parietal cells: gastrin and carbachol induce Ca2+ influx in depleting intracellular Ca2+ stores

Biochemical Journal ◽

10.1042/bj2890117 ◽

1993 ◽

Vol 289 (1) ◽

pp. 117-124 ◽

Cited By ~ 10

Author(s):

S Roche ◽

J P Bali ◽

R Magous

Keyword(s):

Steady State ◽

Receptor Activation ◽

Parietal Cells ◽

The Other ◽

Bivalent Cation ◽

Gtp Binding ◽

Gastric Parietal Cells ◽

Type Receptor ◽

Ca2 Channels ◽

Stimulation Of

The mechanism whereby gastrin-type receptor and muscarinic M3-type receptor regulate free intracellular Ca2+ concentration ([Ca2+]i) was studied in rabbit gastric parietal cells stimulated by either gastrin or carbachol. Both agonists induced a biphasic [Ca2+]i response: a transient [Ca2+]i rise, followed by a sustained steady state depending on extracellular Ca2+. Gastrin and carbachol also caused a rapid and transient increase in Mn2+ influx (a tracer for bivalent-cation entry). Pre-stimulation of cells with one agonist drastically decreased both [Ca2+]i increase and Mn2+ influx induced by the other. Neither diltiazem nor pertussistoxin treatment had any effect on agonist-stimulated Mn2+ entry. Thapsigargin, a Ca(2+)-pump inhibitor, induced a biphasic [Ca2+]i increase, and enhanced the rate of Mn2+ entry. Preincubation of cells with thapsigargin inhibits the [Ca2+]i increase as well as Mn2+ entry stimulated by gastrin or by carbachol. Thapsigargin induced a weak but significant increase in Ins(1,4,5)P3 content, but this agent had no effect on the agonist-evoked Ins(1,4,5)P3 response. In permeabilized parietal cells, Ins(1,4,5)P3 and caffeine caused an immediate Ca2+ release from intracellular pools, followed by a reloading of Ca2+ pools which can be prevented in the presence of thapsigargin. We conclude that (i) gastrin and carbachol mobilize common Ca2+ intracellular stores, (ii) Ca2+ permeability secondary to receptor activation involves neither a voltage-sensitive Ca2+ channel nor a GTP-binding protein from the G1 family, and (iii) agonists regulate common Ca2+ channels in depleting intracellular Ca2+ stores.

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Secretion of gastric parietal cells

Cellular and Molecular Life Sciences ◽

10.1007/bf02159085 ◽

1958 ◽

Vol 14 (6) ◽

pp. 204-205 ◽

Cited By ~ 4

Author(s):

D. Birnbaum ◽

M. Wolman

Keyword(s):

Parietal Cells ◽

Gastric Parietal Cells

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Primary culture of secretagogue-responsive parietal cells from rabbit gastric mucosa

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.1989.256.1.g254 ◽

1989 ◽

Vol 256 (1) ◽

pp. G254-G263 ◽

Cited By ~ 20

Author(s):

C. S. Chew ◽

M. Ljungstrom ◽

A. Smolka ◽

M. R. Brown

Keyword(s):

Gastric Mucosa ◽

Primary Culture ◽

Cultured Cells ◽

Single Cells ◽

Parietal Cells ◽

Ultrastructural Changes ◽

Long Term Effects ◽

H2 Receptor Antagonist ◽

Morphological Transformations

A new procedure for isolation and primary culture of gastric parietal cells is described. Parietal cells from rabbit gastric mucosa are enriched to greater than 95% purity by combining a Nycodenz gradient separation with centrifugal elutriation. Cells are plated on the basement membrane matrix, Matrigel, and maintained in culture for at least 1 wk. Parietal cells cultured in this manner remain differentiated, cross-react with monoclonal H+-K+-ATPase antibodies, and respond to histamine, gastrin, and cholinergic stimulation with increased acid production as measured by accumulation of the weak base, [14C]aminopyrine. When stimulated, cultured cells undergo ultrastructural changes in which intracellular canaliculi expand and numerous microvilli are observed. These ultrastructural changes are similar to those previously found to occur in vivo and in acutely isolated parietal cells. Morphological transformations in living cells can also be observed with differential interference contrast optics in the light microscope. After histamine stimulation, intracellular canaliculi gradually expand to form large vacuolar spaces. When the H2 receptor antagonist, cimetidine, is added to histamine-stimulated cells, these vacuoles gradually disappear. The ability to maintain hormonally responsive parietal cells in primary culture should make it possible to study direct, long-term effects of a variety of agonists and antagonists on parietal cell secretory-related activity. These cultured cells should also prove to be useful for the study of calcium transients, ion fluxes, and intracellular pH as related to acid secretion in single cells, particularly since morphological transformations can be used to monitor "physiological" responses at the same time within the same cell.

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Whole-cell K+ current activation in response to voltages and carbachol in gastric parietal cells isolated from guinea pig

The Journal of Membrane Biology ◽

10.1007/bf01871363 ◽

1991 ◽

Vol 124 (1) ◽

pp. 43-52 ◽

Cited By ~ 12

Author(s):

Tohru Kotera ◽

Akira Hashimoto ◽

Shunji Ueda ◽

Yasunobu Okada

Keyword(s):

Guinea Pig ◽

Parietal Cells ◽

Whole Cell ◽

Current Activation ◽

K Current ◽

Gastric Parietal Cells

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Polarized Distribution of IQGAP Proteins in Gastric Parietal Cells and Their Roles in Regulated Epithelial Cell Secretion

Molecular Biology of the Cell ◽

10.1091/mbc.e02-07-0425 ◽

2003 ◽

Vol 14 (3) ◽

pp. 1097-1108 ◽

Cited By ~ 25

Author(s):

Rihong Zhou ◽

Zhen Guo ◽

Charles Watson ◽

Emily Chen ◽

Rong Kong ◽

...

Keyword(s):

Epithelial Cell ◽

Actin Cytoskeleton ◽

Acid Secretion ◽

Rho Gtpase ◽

Apical Membrane ◽

Basolateral Membrane ◽

Parietal Cells ◽

Actin Dynamics ◽

Cell Secretion ◽

Gastric Parietal Cells

Actin cytoskeleton plays an important role in the establishment of epithelial cell polarity. Cdc42, a member of Rho GTPase family, modulates actin dynamics via its regulators, such as IQGAP proteins. Gastric parietal cells are polarized epithelial cells in which regulated acid secretion occurs in the apical membrane upon stimulation. We have previously shown that actin isoforms are polarized to different membrane domains and that the integrity of the actin cytoskeleton is essential for acid secretion. Herein, we show that Cdc42 is preferentially distributed to the apical membrane of gastric parietal cells. In addition, we revealed that two Cdc42 regulators, IQGAP1 and IQGAP2, are present in gastric parietal cells. Interestingly, IQGAP2 is polarized to the apical membrane of the parietal cells, whereas IQGAP1 is mainly distributed to the basolateral membrane. An IQGAP peptide that competes with full-length IQGAP proteins for Cdc42-binding in vitro also inhibits acid secretion in streptolysin-O-permeabilized gastric glands. Furthermore, this peptide disrupts the association of IQGAP and Cdc42 with the apical actin cytoskeleton and prevents the apical membrane remodeling upon stimulation. We propose that IQGAP2 forms a link that associates Cdc42 with the apical cytoskeleton and thus allows for activation of polarized secretion in gastric parietal cells.

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