同: parietal cells, gastric

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small room in which a monk or nun lives (同)cubicle
a device that delivers an electric current as the result of a chemical reaction (同)electric cell
a room where a prisoner is kept (同)jail cell, prison cell
(biology) the basic structural and functional unit of all organisms; they may exist as independent units of life (as in monads) or may form colonies or tissues as in higher plants and animals
any small compartment; "the cells of a honeycomb"
a small unit serving as part of or as the nucleus of a larger political movement (同)cadre
of or relating to or associated with the parietal bones in the cranium; "parietal lobe"

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(刑務所の)『独房』;(修道院の)小さい独居室 / (ミツバチの)みつ房,巣穴 / 小さい部屋 / 『細胞』 / 電池 / 花粉室 / (共産党などの)細胞
頭頂[骨]の / 大学構内居住に関する

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2014/02/13 05:53:55」(JST)

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Parietal cells (also known as oxyntic or delomorphous cells), are the stomach epithelial cells that secrete gastric acid (HCl) and intrinsic factor. These cells are only located in glands found in a particular area of the stomach, known as the fundus. They contain an extensive secretory network (called canaliculi) from which the HCl is secreted by active transport into the stomach. The enzyme hydrogen potassium ATPase (H⁺/K⁺ ATPase) is unique to the parietal cells and transports the H⁺ against a concentration gradient of about 3 million to 1, which is the steepest ion gradient formed in the human body. Parietal cells are primarily regulated via histamine, acetylcholine and gastrin signaling from both central and local modulators (see 'Regulation').

Secretion of Hydrochloric Acid[edit]

Synthesis[edit]

Hydrochloric acid is formed in the following manner:

Hydrogen ions are formed from the dissociation of water molecules. The enzyme carbonic anhydrase converts one molecule of carbon dioxide and one molecule of water indirectly into a bicarbonate ion (HCO₃^-) and a hydrogen ion (H⁺).
The bicarbonate ion (HCO₃^-) is exchanged for a chloride ion (Cl^-) on the basal side of the cell and the bicarbonate diffuses into the venous blood, leading to an alkaline tide phenomenon.
Potassium (K⁺) and chloride (Cl^-) ions diffuse into the canaliculi.
Hydrogen ions are pumped out of the cell into the canaliculi in exchange for potassium ions, via the H⁺/K⁺ ATPase.

As a result of the cellular export of hydrogen ions, the gastric lumen is maintained as a highly-acidic environment. The acidity aids in digestion of food by promoting the unfolding (or denaturing) of ingested proteins. As proteins unfold, the peptide bonds linking component amino acids are exposed. Gastric HCl simultaneously activates pepsinogen, an endopeptidase that advances the digestive process by breaking the now-exposed peptide bonds, a process known as proteolysis.

Regulation[edit]

Parietal cells secrete acid in response to three types of stimuli:^[1]

Histamine, stimulates H₂ histamine receptors (most significant contribution).
Acetylcholine, from parasympathetic activity via the vagus nerve and enteric nervous system, stimulating M₃ receptors.^[2]
Gastrin, stimulating CCK2 receptors (least significant contribution, but also causes histamine secretion by local ECL cells)

Input through these receptors regulates acid secretion by increasing intracellular levels cAMP and Ca2+ by independent signaling pathways. The histamine receptors act by causing activation of increasing adenylate cyclase in the parietal cell. This increases intracellular cyclic AMP, which leads to activation of protein kinase A. By contrast, the M3 and gastrin receptor pathways lead to protein kinase activation by a different pathway that involves increasing intracellular Ca²⁺ levels. Protein kinase A then phosphorylates proteins involved in the transport of H⁺/K⁺ ATPase from the cytoplasm to the cell membrane. This causes resorption of K⁺ ions and secretion of H⁺ ions. The pH of the secreted fluid can fall by 0.8.

Gastrin primarily induces acid-secretion indirectly, increasing histamine synthesis in ECL cells,which in turn signal parietal cells via histamine release/H2 stimulation.^[3] Gastrin itself has no effect on the maximum histamine-stimulated gastric acid secretion.^[4]

Intrinsic factor[edit]

Parietal cells also produce intrinsic factor. Intrinsic factor is required for the absorption of Vitamin B₁₂ in the diet. A long-term deficiency in vitamin B₁₂ can lead to megaloblastic anemia, characterized by large fragile erythrocytes. Pernicious anemia is a condition where intrinsic factor is not produced and leads to the same type of anemia. Atrophic gastritis, particularly in the elderly, will cause an inability to absorb B₁₂ and can lead to deficiencies such as decreased DNA synthesis and nucleotide metabolism in the bone marrow.

Canaliculus[edit]

A canaliculus is an adaptation found on gastric parietal cells. It is a deep infolding, or little channel, which serves to increase the surface area, e.g. for secretion. The membrane of parietal cells is dynamic; the numbers of canaliculi rise and fall according to secretory need. This is accomplished by the fusion of canalicular precursors, or "tubulovesicles", with the membrane to increase surface area, and the reciprocal endocytosis of the canaliculi (reforming the tubulovesicles) to decrease it.

Diseases of parietal cells[edit]

Immunofluorescence staining pattern of gastric parietal antibodies on a stomach section

Peptic ulcers can result from over-acidity in the stomach. Antacids can be used to enhance the natural tolerance of the gastric lining. Antimuscarinic drugs such as pirenzepine or H₂ antihistamines can reduce acid secretion. Proton pump inhibitors are more potent at reducing gastric acid production since that is the final common pathway of all stimulation of acid production.
In pernicious anemia, autoantibodies directed against parietal cells or intrinsic factor cause a reduction in vitamin B₁₂ absorption. It can be treated with injections of replacement vitamin B₁₂ (methylcobalamin, hydroxocobalamin or cyanocobalamin).
Achlorhydria is another autoimmune disease of the parietal cells. The damaged parietal cells are unable to produce the required amount of gastric acid. This leads to an increase in gastric pH, impaired digestion of food and increased risk of gastroenteritis.

References[edit]

^ Boulpaep, Walter (2009). Medical Physiology. Philadelphia: Saunders. pp. 898–899. ISBN 978-1-4160-3115-4.
^ "Gastric acid secretion - Homo sapiens". KEGG. Retrieved June 1, 2011.
^ Waldum, Helge L., Kleveland, Per M., et al. (2009)'Interactions between gastric acid secretagogues and the localization of the gastrin receptor',Scandinavian Journal of Gastroenterology,44:4,390 — 393
^ Kleveland PM, Waldum HL, Larsson M. Gastric acid secretion in the totally isolated, vascularly perfused rat stomach. A selective muscarinic-1 agent does, whereas gastrin does not, augment maximal histamine-stimulated acid secretion. Scand J Gastroenterol 1987;/22:/705�13.

External links[edit]

Illustration of Chief cells and Parietal cells at anatomyatlases.org
The Parietal Cell: Mechanism of Acid Secretion at vivo.colostate.edu
BU Histology Learning System: 11303loa - Digestive System: Alimentary Canal: fundic stomach, gastric glands, lumen"
Physiology at MCG 6/6ch4/s6ch4_8
Physiology at MCG 6/6ch4/s6ch4_14
Parietal cell antibody
Antibody to GPC

UpToDate Contents

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English Journal

Potassium-induced cortical spreading depression bilaterally suppresses the electroencephalogram but only ipsilaterally affects red blood cell velocity in intraparenchymal capillaries.

Unekawa M, Tomita Y, Toriumi H, Masamoto K, Kanno I, Suzuki N.SourceDepartment of Neurology, School of Medicine, Keio University, Tokyo, Japan. unekawa.m@z5.keio.jp.
Journal of neuroscience research.J Neurosci Res.2013 Apr;91(4):578-84. doi: 10.1002/jnr.23184. Epub 2013 Jan 18.
Cortical spreading depression (CSD) is a repetitive, propagating profile of mass depolarization of neuronal and glial cells, followed by sustained suppression of spontaneous neuronal activity. We have reported a long-lasting suppressive effect on red blood cell (RBC) velocities in intraparenchymal c
PMID 23335342

H+ -K+ -ATPase expression in human parietal cell and gastric acid secretion in elderly.

Zhang W, Zheng SB, Zhuang Y, Xiang P, Xiao L, Li B, Ji DN, Xia SJ, Yu Z, Shi DY.SourceDepartment of Gastroenterology, Huadong Hospital affiliated to Fudan University.
Journal of digestive diseases.J Dig Dis.2013 Mar 5. doi: 10.1111/1751-2980.12055. [Epub ahead of print]
OBJECTIVE: To investigate whether the ultrastructure and H+ -K+ -ATPase expression of human parietal cells are associated with age-related alterations.METHODS: Fifty partipants who underwent gastroscopy due to dyspepsia were enrolled and divided into two age groups, with 19 in the younger group (YG,
PMID 23462150

Lack of cholinergic innervation in the gastric mucosa does not affect gastrin secretion or basal acid output in GFRα2-deficient mice.

Kupari J, Rossi J, Herzig KH, Airaksinen MS.SourceInstitute of Biomedicine, Anatomy, University of Helsinki;
The Journal of physiology.J Physiol.2013 Mar 4. [Epub ahead of print]
Efferent signals from the vagus nerve are thought to mediate both basal and meal-induced gastric acid secretion, and provide trophic support of the mucosa. However, the underlying mechanisms are incompletely understood. Neurturin, signaling via GDNF-family receptor α2 (GFRα2), is essential for par
PMID 23339174

Japanese Journal

胃酸分泌細胞におけるポンプとトランスポーターの分子機能連関 (特集消化管機能の新たなる展開)

藤井拓人,酒井秀紀
京都府立医科大学雑誌 124(4), 231-240, 2015-04
NAID 40020466545

Steroids and Immunosuppressant Agents Do Not Affect Indirect Revascularization in Quasi-Moyamoya Disease Associated with Pure Red Cell Aplasia: A Case Report

Kidani Naoya,Kimura Toshikazu,Ichikawa Yasumitsu,Usuki Kensuke,Morita Akio
NMC Case Report Journal 2(1), 12-15, 2015
… A 31-year-old woman with pure red cell aplasia presented with motor aphasia and right homonymous hemianopia due to a left temporal and parietal lobe infarction. … She was diagnosed with quasi-moyamoya disease and subsequently underwent direct and indirect anastomosis surgery, while continuing steroid and immunosuppressant therapy for pure red cell aplasia. …
NAID 130005056829

Primary Intracerebral Alveolar Soft Part Sarcoma in an 11-Year-Old Girl: Case Report and Review of the Literature

Emmez Hakan,Kale Aydemir,Çelik Sevinç,Börcek Alp Özgün,Yilmaz Güldal,Kaymaz Memduh,Uluoğlu Ömer,Paşaoğlu Aydın
NMC Case Report Journal 2(1), 31-35, 2015
… Alveolar soft part sarcoma (ASPS), a rarely observed tumor, is a soft tissue sarcoma with an unidentified cell origin. … An 11-year-old girl was operated because of fronto-parietal mass lesion by craniotomy. …
NAID 130005056828

Related Pictures

★リンクテーブル★

リンク元	「壁細胞」「傍細胞」
関連記事	「parietal」「cell」

「壁細胞」

Parietal cell
	Human parietal cells (pink staining) - stomach
	Control of stomach acid
Latin	exocrinocytus parietalis
MeSH	Gastric+Parietal+Cells
Code	TH H3.04.02.1.00033