scholarly journals Rapid insertion of GLUT2 into the rat jejunal brush-border membrane promoted by glucagon-like peptide 2

2002 ◽  
Vol 367 (1) ◽  
pp. 247-254 ◽  
Author(s):  
Anita AU ◽  
Alina GUPTA ◽  
Paul SCHEMBRI ◽  
Chris. I. CHEESEMAN
Keyword(s):  
Membrane Proteins ◽  
Western Blotting ◽  
Brush Border ◽  
Brush Border Membrane ◽  
High Capacity ◽  
Intestinal Lumen ◽  
Rat Jejunum ◽  
Frozen Sections ◽  
Glucagon Like Peptide

A possible role for GLUT2 transiently expressed in the rat jejunal brush-border membrane (BBM) under the influence of glucagon-like peptide 2 (GLP-2) was investigated using in vivo perfusion of the intestinal lumen as well as isolation of membrane proteins and immunohistochemistry. A 1h vascular infusion of GLP-2 in vivo doubled the rate of fructose absorption and this increase could be blocked by luminal phloretin. Immunohistochemistry of frozen sections of rat jejunum showed the expression of GLUT2 in both the basolateral and BBMs of mature enterocytes. Perfusion of the intestinal lumen with 50mM d-glucose or vascular infusion of 800pM GLP-2 for 1h increased the expression of GLUT2 in the BBM. Quantification of these changes using Western blotting of biotinylated surface-exposed protein showed a doubling of the expression of GLUT2 in the BBM, but the effects of glucose and GLP-2 were not additive. These results indicate that vascular GLP-2 can promote the insertion of GLUT2 into the rat jejunal BBM providing a low-affinity/high-capacity route of entry for dietary hexoses.

Effects of taurodeoxycholate on in vivo water and solute transport in rat jejunum in absence and presence of calcium

1986 ◽  
Vol 250 (2) ◽  
pp. G248-G251
Author(s):  
H. V. Ammon ◽  
D. S. Cho ◽  
R. L. Loeffler ◽  
K. L. Reetz
Keyword(s):  
Fatty Acids ◽  
Bile Acids ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Calcium Absorption ◽  
Intestinal Transport ◽  
Fluid Secretion ◽  
Rat Jejunum ◽  
Perfusion Studies

Bile acids and fatty acids enhance the permeability of brush-border membrane vesicles for calcium. It has been postulated that increased influx of calcium into the enterocyte might be responsible for the fluid secretion induced by dihydroxy bile acids and fatty acids. During in vivo perfusion studies of the rat jejunum, 15 mM taurodeoxycholate induced secretion of electrolytes and water (P less than 0.001), reduced glucose absorption (P less than 0.001), and enhanced the absorption of mannitol (P less than 0.0125) and calcium (P less than 0.001). Calcium absorption continued to be enhanced during perfusion of a CaCl2-containing solution following the perfusion with taurodeoxycholate (P less than 0.05). In view of the previously demonstrated enhanced permeability of the apical brush-border membrane in the presence of bile acids, it is very likely that some calcium enters the enterocyte along the steep concentration gradient in the presence of taurodeoxycholate. In spite of enhanced calcium absorption, 15 mM CaCl2 had no effect on control absorption rates or on fluid secretion induced by taurodeoxycholate. The data indicate that the effects of bile acids on intestinal transport are not mediated by an influx of calcium into the enterocyte.

Potential differences influence amino acid/Na+ symport rates in larval Manduca sexta midgut brush-border membrane vesicles.

1994 ◽  
Vol 189 (1) ◽  
pp. 55-67
Author(s):  
R Parthasarathy ◽  
W R Harvey
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Manduca Sexta ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Membrane Vesicles ◽  
Brush Border Membrane Vesicles ◽  
Rate Determining Step ◽  
Half Saturation Constant

The time-dependent fluorescence intensity of an intravesicular potential-sensitive dye was used to probe the real-time kinetics of potential difference (PD)-dependent amino acid/Na+ symport at pH9 into brush-border membrane vesicles obtained from larval Manduca sexta midgut. Neutral amino acids (alanine, proline) are symported at higher rates as the vesicles are hyperpolarized. The symport rates of acidic (glutamate) and basic (arginine) amino acids are almost PD-independent. The half-saturation constant of alanine is PD-independent between -108 and -78 mV, although the maximal symport velocity increases by half as the voltage is increased. Amino acid throughput is evidently enhanced as the relatively high transmembrane PDs (> 150 mV, lumen positive) measured in vivo are approached. The half-saturation concentrations of Na+ were in the range 15-40 mmol l-1 for most of the amino acids examined and increased with voltage for alanine. The Vmax observed as a function of cation or amino acid concentration increased as the vesicle was hyperpolarized in the case of leucine and alanine. The data support the hypothesis that carrier and substrates are at equilibrium inasmuch as substrate translocation seems to be the rate-determining step of symport.

Mechanism of maleic acid-induced glucosuria in dog kidney

1976 ◽  
Vol 231 (4) ◽  
pp. 1024-1032 ◽  
Author(s):  
M Silverman ◽  
L Huang
Keyword(s):  
Brush Border ◽  
Maleic Acid ◽  
Brush Border Membrane ◽  
Multiple Indicator Dilution ◽  
Dog Kidney ◽  
Proximal Tubular ◽  
Multiple Indicator ◽  
Prior Administration

The multiple indicator-dilution technique in vivo and isolated brush-border membranes in vitro have been used to explore the mechanism of maleic acid-induced glucosuria in dog kidney. The interaction of D-glucose with the antiluminal membrane from the peritubular fluid surface is unaltered. It is demonstrated that alpha-methyl-D-glucoside (alpha MG) enters and exits from the proximal tubular cell only across the brush-border membrane. Then using alphaMG as a reference indicator, it is shown that maleic acid does not cause complete inhibition of D-glucose interaction with the antiluminal membrane from the cytoplasmic surface. The binding of [3H]phlorizin both in vivo and in vitro is not affected by prior administration of maleic acid, indicating that D-glucose interaction with the outside surface of the brush border is also not affected by maleic acid. The data are therefore consistent with the concept that maleic acid-induced glucosuria is due either to i) partial inhibition of D-glucose movement from cytoplasm across the antiluminal membrane into the blood, ii) stimulated movement back across the brush-border membrane into urine, or iii) a combination of the two effects.

Internalization and intracellular transport of folate-binding protein in rat kidney proximal tubule

1993 ◽  
Vol 264 (2) ◽  
pp. C302-C310 ◽  
Author(s):  
H. Birn ◽  
J. Selhub ◽  
E. I. Christensen
Keyword(s):  
Plasma Membrane ◽  
Proximal Tubule ◽  
Brush Border ◽  
Intracellular Transport ◽  
Brush Border Membrane ◽  
Specific Binding ◽  
Binding Protein ◽  
Rat Kidney ◽  
Folate Binding Protein

Folate-binding protein (FBP) is involved in folate reabsorption in the renal proximal tubule. Immunocytochemical studies have located FBP to the brush-border membrane, endocytic vacuoles, and dense apical tubules. We applied the same polyclonal antibody (anti-FBP) against FBP to investigate the dynamic relationship between FBP in the different compartments by microinjecting the antibody into rat kidney proximal tubules in situ. Specific binding of anti-FBP in vivo to the brush-border membrane was followed by fixation at various times. Protein A-gold labeling shows that anti-FBP is transported from endocytic invaginations into vacuoles followed by transport into dense apical tubules within 15 s. Thus FBP is rapidly internalized, and together with previous studies this study strongly suggests recycling of FBP back to the luminal plasma membrane through dense apical tubules. The results are consistent with reabsorption of folate through endocytosis of the FBP-folate complex followed by dissociation and recycling of FBP. When time is allowed there is a steady accumulation of FBP in dense apical tubules combined with an increase in surface density of the same compartment. A possible explanation involves partial inhibition of the fusion between dense apical tubules and plasma membrane because of the anti-FBP labeling of the receptor.

Transepithelial transport of cholyltaurine by Caco-2 cell monolayers is sodium dependent

1993 ◽  
Vol 264 (6) ◽  
pp. G1118-G1125 ◽  
Author(s):  
C. E. Chandler ◽  
L. M. Zaccaro ◽  
J. B. Moberly
Keyword(s):  
Bile Acids ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Incubation Temperature ◽  
Membrane Vesicles ◽  
Metabolic Inhibitors ◽  
Intestinal Lumen ◽  
Transepithelial Transport ◽  
Reverse Direction ◽  
Dependent Transport

Bile acids are efficiently recovered from the intestinal lumen by a Na(+)-dependent transport process that is localized in the ileal enterocyte brush-border membrane. To establish a cell culture model for this process, we examined the Na+ dependence of cholyltaurine (C-tau; taurocholate) transport across monolayers of differentiated Caco-2 cells grown on permeable filter inserts. Transport of [3H]C-tau was Na+ dependent (> 20-fold stimulation), saturable, and time linear for at least 60 min. The apparent Michaelis constant of [3H]C-tau transport was approximately 65 microM, and the maximal transport rate was approximately 800 pmol.min-1.mg protein-1. Transport of [3H]C-tau in the apical-to-basolateral direction was 17-fold greater than transport in the reverse direction. Lowered incubation temperature, various metabolic inhibitors, and various unlabeled bile acids inhibited [3H]C-tau transport. Caco-2 cells thus transport bile acids in a manner similar to that described for ileal brush-border membrane vesicles and isolated ileal enterocytes and are therefore an appropriate model for studying the molecular basis of ileal bile acid transport.

Indirect coupling of urate and p-aminohippurate transport to sodium in human brush-border membrane vesicles

1996 ◽  
Vol 270 (1) ◽  
pp. F61-F68 ◽  
Author(s):  
F. Roch-Ramel ◽  
B. Guisan ◽  
L. Schild
Keyword(s):  
Brush Border ◽  
Brush Border Membrane ◽  
Membrane Vesicles ◽  
Brush Border Membrane Vesicles ◽  
Indirect Coupling ◽  
Sodium Gradient ◽  
Beta Hydroxybutyrate ◽  
Sodium Cotransport ◽  
Stimulation Of

[14C]urate and p-[14C]aminohippurate (PAH) uptake by human brush-border membrane vesicles (BBMV) were measured in the presence of an inwardly oriented sodium gradient. No direct sodium cotransport was observed. Indirect [14C]urate coupling to sodium transport was demonstrated by cis-stimulation of [14C]urate with nicotinate or pyrazinoate (PZA) in the extravesicular medium but not by adding lactate, alpha-ketoglutarate, or beta-hydroxybutyrate. Indirect sodium coupling of [14C]PAH uptake was observed only when alpha-ketoglutarate was added to the extravesicular medium, a mechanism similar to that of basolateral membranes. The ability for PZA (and nicotinate) to cis-stimulate urate uptake was correlated with a high apparent affinity for the urate/anion exchanger. In urate-loaded vesicles, for identical medium concentrations, [14C]PZA uptake via the urateanion exchanger was 10 times higher than [14C]lactate uptake. Such high PZA affinity for the urate exchanger, working in parallel with PZA sodium cotransport can account for the stimulation of urate reabsorption by PZA in vivo.

scholarly journals The roles of glucagon-like peptide-2 and the intestinal epithelial insulin-like growth factor-1 receptor in regulating microvillus length

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Melanie A. Markovic ◽  
Patricia L. Brubaker
Keyword(s):  
Growth Factor ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Jejunal Mucosa ◽  
Dependent Manner ◽  
Insulin Like Growth Factor ◽  
Intestinal Epithelial ◽  
Glucagon Like Peptide ◽  
Long Acting ◽  
Downstream Mediator

Abstract Microvilli are tiny projections on the apical end of enterocytes, aiding in the digestion and absorption of nutrients. One of their key features is uniform length, but how this is regulated is poorly understood. Glucagon-like peptide-2 (GLP-2) has been shown to increase microvillus length but, the requirement of its downstream mediator, the intestinal epithelial insulin-like growth factor-1 receptor (IE-IGF-1R), and the microvillus proteins acted upon by GLP-2, remain unknown. Using IE-IGF-1R knockout (KO) mice, treated with either long-acting human (h) (GLY2)GLP-2 or vehicle for 11d, it was found that the h(GLY2)GLP-2-induced increase in microvillus length required the IE-IGF-1R. Furthermore, IE-IGF-1R KO alone resulted in a significant decrease in microvillus length. Examination of the brush border membrane proteome as well as of whole jejunal mucosa demonstrated that villin was increased with h(GLY2)GLP-2 treatment in an IE-IGF-1R-dependent manner. Under both basal conditions and with h(GLY2)GLP-2 treatment of the IE-IGF-1R KO mice, changes in villin, IRTKS-1, harmonin, β-actin, and myosin-1a did not explain the decrease in microvillus length, in either the brush border or jejunal mucosa of KO animals. Collectively, these studies define a new role for the IE-IGF-1R within the microvillus, in both the signaling cascade induced by GLP-2, as well as endogenously.

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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