Effect of Na+ on intestinal succinate transport and metabolism in vitro

1988 ◽  
Vol 255 (1) ◽  
pp. C95-C101 ◽  
Author(s):  
A. J. Moe ◽  
R. T. Mallet ◽  
M. J. Jackson ◽  
J. A. Hollywood ◽  
J. K. Kelleher
Keyword(s):  
Brush Border ◽  
Brush Border Membrane ◽  
Tricarboxylic Acid Cycle ◽  
Membrane Vesicles ◽  
Brush Border Membrane Vesicles ◽  
Co2 Production ◽  
Intestinal Brush Border Membrane ◽  
14Co2 Production ◽  
Rat Enterocytes

The effect of Na+ on 14CO2 production from [14C]succinate was studied in isolated rat enterocytes, and Na+-dependent succinate transport was characterized in pig intestinal brush-border membrane vesicles. The production of 14CO2 from [14C]succinate by enterocytes was decreased 12-fold when Na+ was replaced by N-methyl-D-glucamine in the absence of glutamine and 20-fold in the presence of 0.2 or 0.5 mM glutamine. The ratio of 14CO2 produced from [1,4-14C]succinate to that produced by [2,3-14C]succinate was not affected by Na+ replacement, indicating that the pattern of tricarboxylic acid cycle metabolism was not altered. The uptake of [14C]succinate by brush-border membrane vesicles was stimulated 10-fold in the presence of 100 mM NaCl compared with 100 mM KCl. When succinate uptake was corrected to transport into an osmotically sensitive space, the magnitude of the Na+ stimulation was 20-fold. Succinate transport into brush-border membrane vesicles was Na+ dependent, electroneutral, nonconcentrative, with an apparent Na+-succinate coupling ratio of 2:1. Results of this study indicate that Na+-stimulated CO2 production by enterocytes can be explained by the effect of Na+ on succinate transport across the brush-border membrane.

Divalent cations and vitamin B12 uptake by intestinal brush-border membrane vesicles

1980 ◽  
Vol 239 (6) ◽  
pp. G452-G456
Author(s):  
R. C. Beesley ◽  
C. D. Bacheller
Keyword(s):  
Vitamin B12 ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Divalent Cations ◽  
Intrinsic Factor ◽  
Membrane Vesicles ◽  
Brush Border Membrane Vesicles ◽  
Tetraacetic Acid ◽  
Intestinal Brush Border Membrane ◽  
Intestinal Brush Border

Brush-border membrane vesicles from hamster intestine were employed to investigate uptake (binding) of vitamin B12 (B12). Ileal vesicles took up 25 times more B12 than did jejunal vesicles. Uptake of B12 by ileal vesicles was dependent on intrinsic factor (IF) and required Ca2+. Increasing the Ca2+ concentration caused an increase in uptake of B12 reaching a maximum at approximately 8 mM Ca2+. At high Ca2+ concentrations, 6–8 mM, Mg2+ had little effect on uptake of B12. At low Ca2+ concentrations, up to 2 mM, Mg2+ stimulated B12 uptake. Mg2+, Mn2+, and, to a lesser extent, Sr2+ stimulated Ca2+-dependent B12 uptake, but Zn2+, Ba2+, Na+, K+, and La3+ did not. B12 was apparently not metabolized and was bound as IF-B12 complex, which could be removed with (ethylenedinitrilo)tetraacetic acid (EDTA). Our results suggest that two types of divalent cation reactive sites are involved in binding of IF-B12. One is Ca2+ specific. The other is less specific reacting with Mg2+, Mn2+, Sr2+, and perhaps Ca2+ itself, thereby stimulating Ca2+-dependent binding of IF-B12 to its ileal receptor.

Uphill transport of beta-alanine in intestinal brush-border membrane vesicles

1990 ◽  
Vol 259 (3) ◽  
pp. G372-G379 ◽  
Author(s):  
Y. Miyamoto ◽  
H. Nakamura ◽  
T. Hoshi ◽  
V. Ganapathy ◽  
F. H. Leibach
Keyword(s):  
Brush Border ◽  
Brush Border Membrane ◽  
Membrane Vesicles ◽  
Brush Border Membrane Vesicles ◽  
Beta Alanine ◽  
Intestinal Brush Border Membrane ◽  
High Affinity ◽  
Intestinal Brush Border ◽  
Proximal Small Intestine ◽  
Uptake Process

The characteristics of beta-alaline uptake were studied in brush-border membrane vesicles isolated from the proximal small intestine of rabbits and were compared with those of L-alpha-alanine uptake. The uptake of beta-alanine as well as L-alpha-alanine was significantly stimulated by imposing an inwardly directed Na+ gradient. Studies on transstimulation and substrate specificity provide evidence that the transport system serving beta-alanine is distinct from the system serving alpha-alanine. The beta-system also accepts taurine as a substrate. The Na(+)-dependent uptakes of beta-alanine and L-alpha-alanine were differentially influenced by anions. The order in which anions supported uptake was Cl- = SCN- greater than F- greater than NO3- = SO2(-4) for beta-alanine, whereas it was SCN- greater than F- = Cl- = NO3- greater than SO2(-4) for L-alpha-alanine. Cl- appeared to be the preferred anion to support the uptake of beta-alanine. beta-Alanine uptake was greater in the presence of an inwardly directed Cl- gradient than in the presence of Cl- at equal concentrations on both sides of the membrane. The uptake was maximal when a Na+ gradient and a Cl- gradient were present simultaneously. The NaCl gradient-driven beta-alanine uptake was stimulated by an inside-negative K(+)-diffusion potential induced by valinomycin, showing that the uptake process is electrogenic. Stoichiometric analyses suggest that multiple Na+ and one Cl- are associated with the uptake of one beta-alanine molecule. The kinetic study shows that the transporter for beta-alanine is a high-affinity, low-capacity system (Kt = 46 +/- 1 microM; Vmax = 30 +/- 1 pmol.mg protein-1.15 s-1).

D-glucose and L-leucine transport by human intestinal brush-border membrane vesicles

1989 ◽  
Vol 256 (3) ◽  
pp. G618-G623 ◽  
Author(s):  
J. M. Harig ◽  
J. A. Barry ◽  
V. M. Rajendran ◽  
K. H. Soergel ◽  
K. Ramaswamy
Keyword(s):  
Small Intestine ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Membrane Vesicles ◽  
Brush Border Membrane Vesicles ◽  
Transport Systems ◽  
Intestinal Brush Border Membrane ◽  
High Affinity ◽  
Intestinal Brush Border ◽  
Sodium Gradient

This study utilized intestinal brush-border membrane vesicles obtained from organ donor intestine to characterize the absorption of D-glucose and L-leucine in the human intestine. Both D-glucose and L-leucine were taken up by sodium gradient-dependent active transport along the entire length of the small intestine. The relative magnitude of transport for both substrates under sodium gradient conditions followed the order distal jejunum greater than proximal jejunum greater than distal ileum. The number of carrier systems in these brush-border membrane vesicles was estimated by Eadie-Hofstee plot analysis. This analysis revealed that L-leucine was actively transported via a single high-affinity transport system for the length of the human small intestine. In contrast, the transport of D-glucose occurred via a high-affinity system along the length of the intestine and via a low-affinity, high-flux transport system that was limited to the proximal intestine. Both glucose transport systems were sodium dependent and phlorizin sensitive. The locations and apparent kinetic parameters of these transport systems indicated that these systems function efficiently in vivo as important mechanisms for carbohydrate and protein assimilation in humans. The presence of these active transport systems along the entire small intestine explains the formidable capacity for carbohydrate and protein assimilation in humans.

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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