Transcellular transport of calcium and inorganic phosphate in the small intestinal epithelium

1981 ◽  
Vol 240 (6) ◽  
pp. G409-G416 ◽  
Author(s):  
H. Murer ◽  
B. Hildmann
Keyword(s):  
Brush Border ◽  
Inorganic Phosphate ◽  
Membrane Vesicles ◽  
Calcium Flux ◽  
Intestinal Epithelial ◽  
Transcellular Transport ◽  
Lateral Membrane ◽  
Sodium Flux ◽  
Small Intestinal

Transport mechanisms involved in the small intestinal handling of inorganic phosphate and calcium have been studied by different in vitro methods during the last few years. In concordance with studies on intact epithelial preparations, studies with brush-border and basal-lateral membrane vesicles isolated from the small intestinal epithelial cell revealed that transcellular calcium and inorganic phosphate fluxes are coupled to transcellular sodium flux, i.e., secondary active via coupling to the primary active sodium flux. A sodium-coupled mechanism in the brush-border membrane leads to cellular accumulation of inorganic phosphate. A sodium-coupled mechanism leads to extrusion of calcium from the cell into the serosal interstitium. A primary active transport mediated by the Ca-ATPase and located in the basal-lateral membrane also exists for calcium. Regulation of transcellular phosphate and calcium flux proceeds via altered influx rates at the luminal cell pole.

scholarly journals Unique Regulation of Enterocyte Brush Border Membrane Na-Glutamine and Na-Alanine Co-Transport by Peroxynitrite during Chronic Intestinal Inflammation

2019 ◽  
Vol 20 (6) ◽  
pp. 1504 ◽  
Author(s):  
Subha Arthur ◽  
Palanikumar Manoharan ◽  
Shanmuga Sundaram ◽  
M Rahman ◽  
Balasubramanian Palaniappan ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Intestinal Inflammation ◽  
Intestinal Epithelial Cells ◽  
Rabbit Model ◽  
Intestinal Epithelial ◽  
Mechanism Of Inhibition ◽  
Chronic Intestinal Inflammation

Na-amino acid co-transporters (NaAAcT) are uniquely affected in rabbit intestinal villus cell brush border membrane (BBM) during chronic intestinal inflammation. Specifically, Na-alanine co-transport (ASCT1) is inhibited secondary to a reduction in the affinity of the co-transporter for alanine, whereas Na-glutamine co-transport (B0AT1) is inhibited secondary to a reduction in BBM co-transporter numbers. During chronic intestinal inflammation, there is abundant production of the potent oxidant peroxynitrite (OONO). However, whether OONO mediates the unique alteration in NaAAcT in intestinal epithelial cells during chronic intestinal inflammation is unknown. In this study, ASCT1 and B0AT1 were inhibited by OONO in vitro. The mechanism of inhibition of ASCT1 by OONO was secondary to a reduction in the affinity of the co-transporter for alanine, and secondary to a reduction in the number of co-transporters for B0AT1, which were further confirmed by Western blot analyses. In conclusion, peroxynitrite inhibited both BBM ASCT1 and B0AT1 in intestinal epithelial cells but by different mechanisms. These alterations in the villus cells are similar to those seen in the rabbit model of chronic enteritis. Therefore, this study indicates that peroxynitrite may mediate the inhibition of ASCT1 and B0AT1 during inflammation, when OONO levels are known to be elevated in the mucosa.

Characterization of the rabbit renal Na(+)-dicarboxylate cotransporter using antifusion protein antibodies

1996 ◽  
Vol 271 (6) ◽  
pp. C1808-C1816 ◽  
Author(s):  
A. M. Pajor ◽  
N. Sun
Keyword(s):  
Fusion Protein ◽  
Brush Border ◽  
Xenopus Oocytes ◽  
Polyclonal Antibodies ◽  
Membrane Vesicles ◽  
Site Directed Mutagenesis ◽  
In Vitro Translation ◽  
Western Blots ◽  
Renal Brush Border Membrane

Polyclonal antibodies were prepared against the rabbit renal Na(+)-dicarboxylate cotransporter, NaDC-1. The antibodies were raised in chickens against a fusion protein consisting of a 60-amino acid peptide from NaDC-1 and glutathione S-transferase. These antibodies specifically recognized the fusion protein in Western blots and could immunoprecipitate the full-length NaDC-1 after in vitro translation. The antifusion protein antibodies specifically recognized a protein of 63 kDa in rabbit renal brush-border membrane vesicles (BBMV), similar to the predicted mass of 66 kDa. Two proteins of 57 and 115 kDa were recognized in rabbit intestinal brush-border membranes. A protein of 66 kDa was recognized in Xenopus oocytes injected with NaDC-1 cRNA. Enzymatic deglycosylation of rabbit renal BBMV resulted in a decrease in mass by 11 kDa, consistent with N-glycosylation at a single site. Site-directed mutagenesis of the two consensus sequences for N-glycosylation in the NaDC-1 cDNA showed that Asn-576, located near the COOH-terminal, is glycosylated. The nonglycosylated mutant of NaDC-1 exhibited 50% of wild-type succinate transport activity when expressed in Xenopus oocytes, suggesting that glycosylation is not essential for function. The revised secondary structure model of NaDC-1 contains 11 putative transmembrane domains and an extracellular glycosylated COOH-terminal.

Electrogenic 2 Na/1 H antiport in crustacean epithelium is inhibited by a monoclonal antibody

1993 ◽  
Vol 264 (4) ◽  
pp. R804-R810
Author(s):  
H. Gert de Couet ◽  
L. Busquets-Turner ◽  
A. Gresham ◽  
G. A. Ahearn
Keyword(s):  
Brush Border ◽  
Membrane Vesicles ◽  
Structural Similarity ◽  
Protein Band ◽  
Monovalent Cation ◽  
Cation Binding ◽  
Western Blots ◽  
System A ◽  
Published Evidence

We have previously published evidence that suggests that Na/H exchange in crustacean and echinoderm epithelia occurs by an electrogenic antiporter protein with two external cation binding sites that accommodate Na, amiloride, or Ca and display a 2:1 monovalent cation antiport stoichiometry. The present study is an initial investigation into the molecular biology of this invertebrate electrogenic exchanger to ascertain its structural similarity to the analogous vertebrate electroneutral antiport system. A panel of monoclonal antibodies was prepared against components of lobster hepatopancreatic epithelial brush-border membranes and assayed immunohistochemically and by Western blotting. The antibodies were tested further in functional assays for their ability to interfere with electrogenic 2 Na/1 H antiport in isolated hepatopancreatic brush-border membrane vesicles. One cell line was identified producing an antibody that significantly inhibited the electrogenic exchange of cations by these membrane preparations and recognized a single protein band on Western blots of hepatopancreas, antennal gland, and gill epithelia corresponding to a molecular mass of 185 kDa. The existence of such an antibody probe may facilitate the purification of the electrogenic antiporter under denaturing conditions, in in vitro expression systems, or in prokaryotic expression libraries.

In vitro Gastrointestinal Models for Prebiotic Carbohydrates: A Critical Review

2019 ◽  
Vol 25 (32) ◽  
pp. 3478-3483 ◽  
Author(s):  
Oswaldo Hernandez-Hernandez
Keyword(s):  
Small Intestine ◽  
Gastrointestinal Tract ◽  
Brush Border ◽  
Critical Review ◽  
In Vitro Digestibility ◽  
Human Gastrointestinal Tract ◽  
Intestinal Brush Border ◽  
Small Intestinal ◽  
Existing Data

Background: In the last decade, various consortia and companies have created standardized digestion protocols and gastrointestinal simulators, such as the protocol proposed by the INFOGEST Consortium, the simulator SHIME, the simulator simgi®, the TIM, etc. Most of them claim to simulate the entire human gastrointestinal tract. However, few results have been reported on the use of these systems with potential prebiotic carbohydrates. Methods: This critical review addresses the existing data on the analysis of prebiotic carbohydrates by different in vitro gastrointestinal simulators, the lack of parameters that could affect the results, and recommendations for their enhancement. Results: According to the reviewed data, there is a lack of a realistic approximation of the small intestinal conditions, mainly because of the absence of hydrolytic conditions, such as the presence of small intestinal brush border carbohydrases that can affect the digestibility of different carbohydrates, including prebiotics. Conclusion: There is a necessity to standardize and enhance the small intestine simulators to study the in vitro digestibility of carbohydrates.

Transport of glucose and leucine by intestinal membrane vesicles in genetic diabetes

1980 ◽  
Vol 238 (5) ◽  
pp. G419-G423 ◽  
Author(s):  
R. Bennetts ◽  
K. Ramaswamy
Keyword(s):  
Brush Border ◽  
Brush Border Membrane ◽  
Membrane Vesicles ◽  
Diabetic Mice ◽  
Drug Induced ◽  
Intestinal Brush Border Membrane ◽  
Intestinal Brush Border ◽  
Intestinal Membrane ◽  
Small Intestinal ◽  
Genetically Diabetic Mice

Na+-dependent D-glucose and L-leucine uptakes by isolated small intestinal brush-border membrane vesicles were studied in normal and genetically diabetic mice (C57BL/KsJ-dbm). Vesicles from normal mice demonstrated transport characteristics and morphological appearances identical to those from other mammalian small intestinal brush-border membrane isolates. There was no difference found between genetically diabetic mice and their littermate controls. These data suggest that the small intestinal brush-border membrane transport is not altered in genetic diabetes in contrast to that found in drug-induced diabetes.

Cholera toxin facilitates calcium transport in jejunal brush border vesicles

1986 ◽  
Vol 64 (5) ◽  
pp. 568-574 ◽  
Author(s):  
David D. Maenz ◽  
G. W. Forsyth
Keyword(s):  
Cholera Toxin ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Equilibrium Dialysis ◽  
Membrane Vesicles ◽  
Second Messenger ◽  
Brush Border Membrane Vesicles ◽  
Ionophore A23187

Cholera toxin is very well characterized in terms of the activation of adenylate cyclase. In some systems, however, this cyclase activation does not seem to account for all of the physiological responses to the toxin. On the premise that cholera toxin may also exert effects through other second messenger compounds we have studied the effect of cholera toxin on the rate of Ca2+ movement across the membrane of intestinal brush border vesicles. Increasing concentrations of cholera toxin progressively accelerated the passive uptake of Ca2+ into, and the efflux of Ca2+ from, an osmotically active space in brush border membrane vesicles. This effect of cholera toxin was saturable by excess Ca2+ and was relatively specific, as the toxin did not affect vesicle permeability to an uncharged polar solute. The toxin had two high affinity Ca2+ binding sites on the A subunit as measured by equilibrium dialysis. Ca2+ transport facilitated by cholera toxin was temperature dependent, required the holotoxin, and could be inhibited by preincubation of the toxin with excess free ganglioside GM1.This increased rate of Ca2+ influx caused by the in vitro addition of cholera toxin to brush border membrane vesicles may have physiological significance as it was comparable to rates observed with the Ca ionophore A23187. Similar effects occurring in vivo could permit cholera toxin to increase cytoplasmic Ca2+ concentrations and to produce accompanying second messenger effects.

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