Regional specificity of iron uptake by small intestinal brush-border membranes from normal and iron-deficient mice

1985 ◽  
Vol 248 (3) ◽  
pp. G376-G379 ◽  
Author(s):  
A. Muir ◽  
U. Hopfer
Keyword(s):  
Brush Border ◽  
Iron Uptake ◽  
Iron Absorption ◽  
Membrane Vesicles ◽  
Soluble Form ◽  
Brush Border Membranes ◽  
Intestinal Brush Border ◽  
Iron Deficient ◽  
Small Intestinal ◽  
Deficient Mice

Fe(II)-ascorbate uptake by purified small intestinal brush-border membrane vesicles prepared from proximal and distal segments was studied in normal and iron-deficient mice. Iron was maintained in a reduced, soluble form by a 20-fold excess of ascorbate at a physiological pH of 7.2-7.4. In normal mice, iron uptake by proximal membrane vesicles was three- to fourfold greater (approximately 1,700 pmol/mg prot) than from distal segments (approximately 500 pmol/mg prot). In iron-deficient mice, uptake of Fe(II) was also greater in proximal membranes (approximately 3,200 pmol/mg prot) than uptake from distal segments (approximately 350 pmol/mg prot), and the regional difference was almost 10-fold, without any change in distal segmental iron uptake. These results are consistent with the pattern of intestinal iron absorption in iron-replete and iron-deficient animals and indicate that regulatory changes in proximal intestinal brush-border membranes may account for the increased iron absorption known to occur in iron deficiency.

Ecto-adenosinetriphosphatase in rat small intestinal brush-border membranes

1995 ◽  
Vol 268 (4) ◽  
pp. G663-G672 ◽  
Author(s):  
C. Schweickhardt ◽  
I. Sabolic ◽  
D. Brown ◽  
G. Burckhardt
Keyword(s):  
Rat Liver ◽  
Brush Border ◽  
Atp Hydrolysis ◽  
Physiological Role ◽  
Membrane Vesicles ◽  
Apical Surface ◽  
Western Blots ◽  
Brush Border Membranes ◽  
Intestinal Brush Border ◽  
Small Intestinal

Antibodies against the holo ecto-adenosinetriphosphatase (ATPase) of rat liver and antibodies against COOH-terminal peptides of the long isoform of this enzyme reacted in Western blots with a 105-kDa band from small intestinal brush-border membranes. Indirect immunofluorescence revealed reactive proteins predominantly at the apical surface of enterocytes with some staining of basolateral membranes and of vascular endothelium. Similar results were obtained with monoclonal antibodies against HA4, a protein from rat liver closely related to the ecto-ATPase. Since these results suggested the presence of an ecto-ATPase, ATP hydrolysis was studied in intact, right-side-out brush-border membrane vesicles. Nearly half of ATP hydrolysis was caused by alkaline phosphatase (AP). Besides purine and pyrimidine trinucleotides, AP also hydrolyzed ADP, AMP, pyrophosphate, and 4-nitrophenylphosphate. Inactivation of AP by cleavage of its membrane anchor and by removal of the Zn2+ necessary for its function left the ecto-ATPase that was activated by Ca2+ and Mg2+ and hydrolyzed purine and pyrimidine trinucleotides and dinucleotides, but not AMP, pyrophosphate, and 4-nitrophenylphosphate. These features are characteristic of an ATP diphosphohydrolase (EC 3.6.1.5, also called apyrase). The physiological role of the small intestinal ecto-ATPase may be the degradation of nutrient nucleotides.

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.

scholarly journals Identification of Na+,Pi-binding protein in kidney and intestinal brush-border membranes

1988 ◽  
Vol 255 (1) ◽  
pp. 185-191 ◽  
Author(s):  
H Debiec ◽  
R Lorenc
Keyword(s):  
Molecular Mass ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Binding Protein ◽  
Polyacrylamide Gel Electrophoresis ◽  
Gel Filtration ◽  
Membrane Vesicles ◽  
High Specificity ◽  
Brush Border Membranes ◽  
Intestinal Brush Border

An Na+, Pi-binding protein has been extracted from kidney and intestinal brush-border membranes with an organic solvent and has been purified by Kieselghur and Sephadex LH-60 chromatography. The molecular mass of this protein has been estimated to be about 155 kDa as determined by gel-filtration chromatography on Sepharose 2B. Under denaturing conditions, polyacrylamide-gel electrophoresis revealed a monomer of molecular mass about 70 kDa. The protein has high specificity and high affinity for Pi [K0.5 (concentration at which half-maximal binding is observed) near 10 microM]. Na2+ binding also exhibits saturation behaviour, with a K0.5 near 7.5 mM. Pi binding is inhibited by known inhibitors of Pi transport in brush-border membrane vesicles. It appears that this protein could be involved in Na+/Pi co-transport across the renal and intestinal brush-border membranes.

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