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Bicarbonate secretion

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https://www.readbyqxmd.com/read/28882824/a-physics-based-model-for-maintenance-of-the-ph-gradient-in-the-gastric-mucus-layer
#1
Owen L Lewis, James P Keener, Aaron L Fogelson
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 auto-digestion 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...
September 7, 2017: American Journal of Physiology. Gastrointestinal and Liver Physiology
https://www.readbyqxmd.com/read/28877883/versatility-of-nacl-transport-mechanisms-in-the-cortical-collecting-duct
#2
Aurélie Edwards, Gilles Crambert
The cortical collecting duct (CCD) forms part of the aldosterone-sensitive distal nephron and plays an essential role in maintaining the NaCl balance and acid-base status. The CCD epithelium comprises principal cells as well as different types of intercalated cells. Until recently, transcellular Na+ transport was thought to be restricted to principal cells, while (acid-secreting) type A and (bicarbonate-secreting) type B intercalated cells were associated with the regulation of acid-base homeostasis. This review describes how this traditional view has been upended by several discoveries in the last decade...
September 6, 2017: American Journal of Physiology. Renal Physiology
https://www.readbyqxmd.com/read/28844960/bile-acid-receptors-in-the-biliary-tree-tgr5-in-physiology-and-disease
#3
REVIEW
Kathleen Deutschmann, Maria Reich, Caroline Klindt, Carola Dröge, Lina Spomer, Dieter Häussinger, Verena Keitel
Bile salts represent signalling molecules with a variety of endocrine functions. Bile salt effects are mediated by different receptor molecules, comprising ligand-activated nuclear transcription factors as well as G protein-coupled membrane-bound receptors. The farnesoid X receptor (FXR) and the plasma membrane-bound G protein-coupled receptor TGR5 (Gpbar-1) are prototypic bile salt receptors of both classes and are highly expressed in the liver including the biliary tree as well as in the intestine. In liver, TGR5 is localized in different non-parenchymal cells such as sinusoidal endothelial cells, Kupffer cells, hepatic stellate cells and small and large cholangiocytes...
August 24, 2017: Biochimica et Biophysica Acta
https://www.readbyqxmd.com/read/28834043/importance-of-bicarbonate-transport-in-ph-control-during-amelogenesis-need-for-functional-studies
#4
G Varga, P DenBesten, R Rácz, Á Zsembery
Dental enamel, the hardest mammalian tissue, is produced by ameloblasts. Ameloblasts show many similarities to other transporting epithelia although their secretory product, the enamel matrix, is quite different. Ameloblasts direct the formation of hydroxyapatite crystals, which liberate large quantities of protons that then need to be buffered to allow mineralization to proceed. Buffering requires a tight pH regulation and secretion of bicarbonate by ameloblasts. Many investigations have used immunohistochemical and knockout studies to determine the effects of these genes on enamel formation, but up till recently very little functional data were available for mineral ion transport...
August 18, 2017: Oral Diseases
https://www.readbyqxmd.com/read/28795233/bicarbonate-transport-during-enamel-maturation
#5
REVIEW
Kaifeng Yin, Michael L Paine
Amelogenesis (tooth enamel formation) is a biomineralization process consisting primarily of two stages (secretory stage and maturation stage) with unique features. During the secretory stage, the inner epithelium of the enamel organ (i.e., the ameloblast cells) synthesizes and secretes enamel matrix proteins (EMPs) into the enamel space. The protein-rich enamel matrix forms a highly organized architecture in a pH-neutral microenvironment. As amelogenesis transitions to maturation stage, EMPs are degraded and internalized by ameloblasts through endosomal-lysosomal pathways...
August 9, 2017: Calcified Tissue International
https://www.readbyqxmd.com/read/28775098/influenza-virus-infection-alters-ion-channel-function-of-airway-and-alveolar-cells-mechanisms-and-physiological-sequelae
#6
James D Londino, Ahmed Lazrak, James F Collawn, Zsuzsanna Bebok, Kevin S Harrod, Sadis Matalon
The cystic fibrosis transmembrane conductance regulator (CFTR) and the amiloride-sensitive epithelial sodium channels (ENaC) are located in the apical membranes of airway and alveolar epithelial cells. These transporters play an important role in the regulation of lung fluid balance across airway and alveolar epithelia by being the conduits for chloride (Cl(-)) and bicarbonate (HCO3(-)) secretion and sodium (Na(+)) ion absorption, respectively. The functional role of these channels in the respiratory tract is to maintain the optimum volume and ionic composition of the bronchial pericilary fluid (PCL) and alveolar lining fluid (ALF) layers...
August 3, 2017: American Journal of Physiology. Lung Cellular and Molecular Physiology
https://www.readbyqxmd.com/read/28774999/sexual-dimorphic-pattern-of-renal-transporters-and-electrolyte-homeostasis
#7
Luciana C Veiras, Adriana C C Girardi, Joshua Curry, Lei Pei, Donna L Ralph, An Tran, Regiane C Castelo-Branco, Nuria Pastor-Soler, Cristina T Arranz, Alan S L Yu, Alicia A McDonough
Compared with males, females have lower BP before age 60, blunted hypertensive response to angiotensin II, and a leftward shift in pressure natriuresis. This study tested the concept that this female advantage associates with a distinct sexual dimorphic pattern of transporters along the nephron. We applied quantitative immunoblotting to generate profiles of transporters, channels, claudins, and selected regulators in both sexes and assessed the physiologic consequences of the differences. In rats, females excreted a saline load more rapidly than males did...
August 3, 2017: Journal of the American Society of Nephrology: JASN
https://www.readbyqxmd.com/read/28771454/%C3%AE-ketoglutarate-drives-electroneutral-nacl-reabsorption-in-intercalated-cells-by-activating-a-g-protein-coupled-receptor-oxgr1
#8
Paul R Grimm, Paul A Welling
PURPOSE OF REVIEW: This review describes the recent discoveries about a powerful electroneutral NaCl reabsorption mechanism in intercalated cells, and its regulation by an intrarenal metabolite paracrine, α-ketoglutartate, and the G-protein coupled receptor, Oxgr1. RECENT FINDINGS: The distal nephron fine-tunes sodium, chloride, potassium, hydrogen, bicarbonate and water transport to maintain electrolyte homeostasis and blood pressure. Intercalated cells have been traditionally viewed as the professional regulators of acid-base balance, but recent studies reveal that a specific population of intercalated cells, identified by the pendrin-transporter, have a surprising role in the regulation of salt balance...
September 2017: Current Opinion in Nephrology and Hypertension
https://www.readbyqxmd.com/read/28732801/bicarbonate-in-cystic-fibrosis
#9
REVIEW
Karl Kunzelmann, Rainer Schreiber, Hans Beat Hadorn
BACKGROUND: Cystic fibrosis (CF, mucoviscidosis) is caused by mutations in the gene encoding CF transmembrane conductance regulator (CFTR), which is a chloride and bicarbonate channel necessary for fluid secretion and extracellular alkalization. For a long time, research concentrated on abnormal Cl(-) and Na(+) transport, but neglected bicarbonate as a crucial factor in CF. METHODS: The present short review reports early findings as well as recent insights into the role of CFTR for bicarbonate transport and its defects in CF...
July 18, 2017: Journal of Cystic Fibrosis: Official Journal of the European Cystic Fibrosis Society
https://www.readbyqxmd.com/read/28706773/why-doesn-t-primary-biliary-cholangitis-respond-to-immunosuppressive-medications
#10
REVIEW
Antonio Molinaro, Hanns-Ulrich Marschall
PURPOSE OF REVIEW: The purpose of this review is to discuss reasons why immunosuppressive therapy so far failed in Primary Biliry Cholangitis. RECENT FINDINGS: Even targeted immunosuppressive therapy seems ineffective or potentially harmful. SUMMARY: Bile acid-mediated cholangiocyte damage, facilitated by insufficient bicarbonate secretion, seems to attenuate the anti-inflammatory and anti-fibrotic actions of immunosuppressant and immunomodulatory drugs in a clinically significant way...
2017: Current Hepatology Reports
https://www.readbyqxmd.com/read/28648509/pendred-syndrome
#11
REVIEW
Jean-Louis Wémeau, Peter Kopp
Pendred syndrome is an autosomal recessive disorder that is classically defined by the combination of sensorineural deafness/hearing impairment, goiter, and an abnormal organification of iodide with or without hypothyroidism. The hallmark of the syndrome is the impaired hearing, which is associated with inner ear malformations such as an enlarged vestibular aqueduct (EVA). The thyroid phenotype is variable and may be modified by the nutritional iodine intake. Pendred syndrome is caused by biallelic mutations in the SLC26A4/PDS gene, which encodes the multifunctional anion exchanger pendrin...
March 2017: Best Practice & Research. Clinical Endocrinology & Metabolism
https://www.readbyqxmd.com/read/28596649/use-of-surrogate-samples-to-monitor-ph-during-high-dose-methotrexate-therapy
#12
Uday Yanamandra, Pooja Chauhan, Deepesh Lad, Alka Khadwal, Gaurav Prakash, Subhash Varma, Pankaj Malhotra
High dose methotrexate (Mtx) therapy is commonly used in hemato-oncological practice. Alkalization of urine is a part of high dose methotrexate therapy for preventing crystallization in urine to avert renal insufficiency. Alkalization is monitored by urine pH at regular intervals. Oral pH has occasionally been used as a surrogate for oral mucositis. To compare and correlate pH of various body secretions (venous blood, oral salivary, lacrimal and urine) among patients undergoing alkalization with intravenous sodium bicarbonate during high dose methotrexate therapy...
June 2017: Indian Journal of Hematology & Blood Transfusion
https://www.readbyqxmd.com/read/28577107/interaction-of-constitutive-nitric-oxide-synthases-with-cyclooxygenases-in-regulation-of-bicarbonate-secretion-in-the-gastric-mucosa
#13
V A Zolotarev, Yu V Andreeva, E Vershinina, R P Khropycheva
Neuronal NO synthase blocker 7-nitroindazole suppressed bicarbonate secretion in rat gastric mucosa induced by mild local irritation with 1 M NaCl (pH 2.0). Non-selective blocker of neuronal and endothelial synthases, Nω-nitro-L-arginine (L-NNA), did not affect HCO3(-) production, but inhibited secretion after pretreatment with omeprazole. Non-selective cyclooxygenase blocker indomethacin inhibited HCO3(-) production under conditions of normal synthase activity and in the presence of L-NNA, but was ineffective when co-administered with 7-nitroindazole...
June 3, 2017: Bulletin of Experimental Biology and Medicine
https://www.readbyqxmd.com/read/28526688/loss-of-the-anion-exchanger-dra-slc26a3-or-pat1-slc26a6-alters-sulfate-transport-by-the-distal-ileum-and-overall-sulfate-homeostasis
#14
Jonathan M Whittamore, Marguerite Hatch
The ileum is considered the primary site of inorganic sulfate ([Formula: see text]) absorption. In the present study, we explored the contributions of the apical chloride/bicarbonate (Cl(-)/[Formula: see text]) exchangers downregulated in adenoma (DRA; Slc26a3), and putative anion transporter 1 (PAT1; Slc26a6), to the underlying transport mechanism. Transepithelial (35)[Formula: see text] and (36)Cl(-) fluxes were determined across isolated, short-circuited segments of the distal ileum from wild-type (WT), DRA-knockout (KO), and PAT1-KO mice, together with measurements of urine and plasma sulfate...
September 1, 2017: American Journal of Physiology. Gastrointestinal and Liver Physiology
https://www.readbyqxmd.com/read/28526687/ffa2-activation-combined-with-ulcerogenic-cox-inhibition-induces-duodenal-mucosal-injury-via-the-5-ht-pathway-in-rats
#15
Yasutada Akiba, Koji Maruta, Kazuyuki Narimatsu, Hyder Said, Izumi Kaji, Ayaka Kuri, Ken-Ichi Iwamoto, Atsukazu Kuwahara, Jonathan D Kaunitz
Serotonin (5-HT), predominantly synthesized and released by enterochromaffin cells, is implicated in gastrointestinal symptoms such as emesis, abdominal pain, and diarrhea. Because luminal short-chain fatty acids (SCFAs) release 5-HT from enterochromaffin cells, which express the SCFA receptor free fatty acid receptor 2 (FFA2) in rat duodenum, we examined the effects of the selective FFA2 agonist phenylacetamide-1 (PA1) on duodenal 5-HT release with consequent bicarbonate secretion [duodenal bicarbonate secretion (DBS)] and on indomethacin (IND)-induced enteropathy...
August 1, 2017: American Journal of Physiology. Gastrointestinal and Liver Physiology
https://www.readbyqxmd.com/read/28523577/ffa3-activation-stimulates-duodenal-bicarbonate-secretion-and-prevents-nsaid-induced-enteropathy-via-the-glp-2-pathway-in-rats
#16
Hyder Said, Yasutada Akiba, Kazuyuki Narimatsu, Koji Maruta, Ayaka Kuri, Ken-Ichi Iwamoto, Atsukazu Kuwahara, Jonathan D Kaunitz
BACKGROUND: Therapy with nonsteroidal anti-inflammatory drugs (NSAIDs) is associated with enteropathy in humans and experimental animals, a cause of considerable morbidity. Unlike foregut NSAID-associated mucosal lesions, most treatments for this condition are of little efficacy. We propose that the endogenously released intestinotrophic hormone glucagon-like peptide-2 (GLP-2) prevents the development of NSAID-induced enteropathy. Since the short-chain fatty acid receptor FFA3 is expressed on enteroendocrine L cells and on enteric nerves in the gastrointestinal tract, we further hypothesized that activation of FFA3 on L cells protects the mucosa from injury via GLP-2 release with enhanced duodenal HCO3(-) secretion...
August 2017: Digestive Diseases and Sciences
https://www.readbyqxmd.com/read/28455748/ck2-is-a-key-regulator-of-slc4a2-mediated-cl-hco3-exchange-in-human-airway-epithelia
#17
Salam H Ibrahim, Mark J Turner, Vinciane Saint-Criq, James Garnett, Iram J Haq, Malcolm Brodlie, Chris Ward, Christian Borgo, Mauro Salvi, Andrea Venerando, Michael A Gray
Transepithelial bicarbonate secretion by human airway submucosal glands and surface epithelial cells is crucial to maintain the pH-sensitive innate defence mechanisms of the lung. cAMP agonists stimulate HCO3(-) secretion via coordinated increases in basolateral HCO3(-) influx and accumulation, as well as CFTR-dependent HCO3(-) efflux at the luminal membrane of airway epithelial cells. Here, we investigated the regulation of a basolateral located, DIDS-sensitive, Cl(-)/HCO3(-) exchanger, anion exchanger 2 (AE2; SLC4A2) which is postulated to act as an acid loader, and therefore potential regulator of HCO3(-) secretion, in human airway epithelial cells...
April 28, 2017: Pflügers Archiv: European Journal of Physiology
https://www.readbyqxmd.com/read/28436589/short-chain-fatty-acids-augment-rat-duodenal-mucosal-barrier-function
#18
Wan Salman Wan Saudi, Markus Sjöblom
What is the central question of this study? Small intestinal epithelium is exposed to high concentrations of short-chain fatty acids (SCFAs), but their role in regulating intestinal mucosal barrier function and motility is not fully understood. What is the main finding and its importance? By perfusing the duodenal segment in anaesthetized rats, we show that acetate and propionate significantly decrease mucosal paracellular permeability and transepithelial net fluid flux and increase mucosal bicarbonate secretion...
April 24, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/28385297/renal-tubular-nhe3-is-required-in-the-maintenance-of-water-and-sodium-chloride-homeostasis
#19
Robert A Fenton, Søren B Poulsen, Samantha de la Mora Chavez, Manoocher Soleimani, Jessica A Dominguez Rieg, Timo Rieg
The sodium/proton exchanger isoform 3 (NHE3) is expressed in the intestine and the kidney, where it facilitates sodium (re)absorption and proton secretion. The importance of NHE3 in the kidney for sodium chloride homeostasis, relative to the intestine, is unknown. Constitutive tubule-specific NHE3 knockout mice (NHE3(loxloxCre)) did not show significant differences compared to control mice in body weight, blood pH or bicarbonate and plasma sodium, potassium, or aldosterone levels. Fluid intake, urinary flow rate, urinary sodium/creatinine, and pH were significantly elevated in NHE3(loxloxCre) mice, while urine osmolality and GFR were significantly lower...
August 2017: Kidney International
https://www.readbyqxmd.com/read/28384243/neuropeptide-s-reduces-duodenal-bicarbonate-secretion-and-ethanol-induced-increases-in-duodenal-motility-in-rats
#20
Wan Salman Wan Saudi, Markus Sjöblom
Alcohol disrupts the intestinal mucosal barrier by inducing metabolic and functional changes in epithelial cells. Recently, we showed that neuropeptide S (NPS) decreases duodenal motility and increases mucosal paracellular permeability, suggesting a role of NPS in the pathogenesis of disorders and dysfunctions in the small intestine. The aim of the present study was to investigate the effects of NPS on ethanol- and HCl-induced changes of duodenal mucosal barrier function and motility. Rats were anaesthetized with thiobarbiturate, and a 30-mm segment of the proximal duodenum with an intact blood supply was perfused in situ...
2017: PloS One
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