Iron uptake from transferrin and lactoferrin by rat intestinal brush-border membrane vesicles

1990 ◽  
Vol 258 (4) ◽  
pp. G535-G541 ◽  
Author(s):  
H. Kawakami ◽  
S. Dosako ◽  
B. Lonnerdal
Keyword(s):  
Brush Border ◽  
Brush Border Membrane ◽  
Specific Binding ◽  
Membrane Vesicles ◽  
Brush Border Membrane Vesicles ◽  
Human Lactoferrin ◽  
Affinity Constant ◽  
Bovine Lactoferrin ◽  
Intestinal Brush Border Membrane ◽  
Intestinal Brush Border

Interaction of 59Fe-labeled rat transferrin, human lactoferrin, and bovine lactoferrin with rat small intestinal brush-border membrane vesicles was investigated with the use of a rapid filtration technique. Specific binding of 59Fe-labeled rat transferrin and bovine lactoferrin to brush-border membrane vesicles from suckling and adult rats was identified. In contrast, no binding of human lactoferrin occurred. The presence of transferrin receptors on the brush-border membrane of suckling rats was confirmed by immunoblotting, and the molecular mass of the receptor was 96 kDa under nonreducing conditions. Scatchard plot analysis indicated 2.4 x 10(14) binding sites/mg of membrane protein with an affinity constant (Ka) of 4.9 x 10(6) M-1 for rat milk transferrin and 2.2 x 10(14) bi

Na-dependent D-glucose and L-alanine transport in eel intestinal brush border membrane vesicles

1986 ◽  
Vol 251 (3) ◽  
pp. R463-R469 ◽  
Author(s):  
C. Storelli ◽  
S. Vilella ◽  
G. Cassano
Keyword(s):  
Glucose Uptake ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Membrane Vesicles ◽  
Brush Border Membrane Vesicles ◽  
Transport Systems ◽  
Affinity Constant ◽  
Intestinal Brush Border Membrane ◽  
Intestinal Brush Border ◽  
Alanine Transport

Brush border membrane vesicles (BBMV) were prepared from eel (Anguilla anguilla) intestine by a Mg-ethylene-glycol-bis(beta-aminoethylether)-N,N'-tetraacetic acid precipitation technique; the BBMV were enriched 16, 12, and 13 times in leucine aminopeptidase, maltase, and alkaline phosphatase activities with respect to the starting mucosal scraping. D-[3H]glucose and L-[3H]alanine transport by these vesicles was studied by a rapid filtration technique. D-Glucose uptake was stimulated by a transmembrane Na gradient but not by an identical Na gradient in the presence of phloridzin or by a choline gradient. The Na-dependent D-glucose uptake was increased by rendering the vesicle interior electrically negative, suggesting electrogenic cotransport of the sugar with Na+. Kinetic analysis gave an apparent affinity constant (Kapp) of 0.20 mM and maximal rate (Jmax) of 6.87 nmol X mg protein-1 X min-1 for glucose influx in the presence of a Na gradient. In addition, a significant apparent diffusional permeability of these membranes to glucose (1.41 microliters X mg protein-1 X min-1) was observed. L-Alanine uptake in eel BBMV was shown to occur via 1) saturable Na-dependent pathway (Kapp = 1.29 mM, Jmax = 3.61 nmol X mg protein-1 X min-1), 2) a saturable Na-independent pathway (Kapp = 0.59, Jmax = 1.49), and 3) a nonsaturable component representing apparent diffusion (permeability coefficient P = 0.57 microliter X mg protein-1 X min-1). These findings suggest that similar transport systems for glucose and alanine are found in the fish and mammalian intestinal 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.

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