Substrate and inhibitor specificity of anion exchangers on the brush border membrane of rabbit ileum

1985 ◽  
Vol 88 (2) ◽  
pp. 199-204 ◽  
Author(s):  
Roy G. Knickelbein ◽  
Peter S. Aronson ◽  
John W. Dobbins
Keyword(s):  
Brush Border ◽  
Brush Border Membrane ◽  
Rabbit Ileum ◽  
Anion Exchangers ◽  
Inhibitor Specificity

cDNA cloning and localization of a band 3-related protein from ileum

1992 ◽  
Vol 263 (3) ◽  
pp. G345-G352 ◽  
Author(s):  
A. Chow ◽  
J. W. Dobbins ◽  
P. S. Aronson ◽  
P. Igarashi
Keyword(s):  
Brush Border ◽  
Brush Border Membrane ◽  
Basolateral Membrane ◽  
Membrane Vesicles ◽  
Band 3 ◽  
Related Protein ◽  
Rabbit Ileum ◽  
Molecular Identity ◽  
Polymerase Chain ◽  
Related Proteins

A Cl(-)-HCO3- exchanger in the brush-border membrane mediates active Cl- absorption and regulates intracellular pH in rabbit ileum. The molecular identity of the ileal Cl(-)-HCO3- exchanger has not been established. The best-characterized plasma membrane Cl(-)-HCO3- exchanger is erythroid band 3. Structurally related proteins in nonerythroid tissues comprise an anion exchanger (AE) family. We used the polymerase chain reaction to amplify and clone a cDNA encoding an ileal band 3-related protein (B3RP) from rabbit ileal enterocytes. The composite sequence is 3,909 bp and is predicted to encode a protein of 136 kDa. The deduced amino acid sequence is 95% identical to murine renal AE2, indicating that ileal B3RP is rabbit AE2. Antisera generated against a cytoplasmic fragment of ileal B3RP recognized a 160- to 170-kDa polypeptide in the brush-border membrane, but not the basolateral membrane, of ileal crypt and villus enterocytes. This correlates with previous studies indicating that a Cl(-)-HCO3- exchange is present in brush-border but not basolateral membrane vesicles from rabbit ileal enterocytes. We conclude that ileal B3RP is a product of the AE gene family, and is present in the brush-border of ileal enterocytes, where it may mediate Cl(-)-HCO3- exchange.

Effects of cations on pH gradient-stimulated sulfate transport in rabbit ileal brush-border membrane vesicles

1985 ◽  
Vol 249 (5) ◽  
pp. G614-G621 ◽  
Author(s):  
C. M. Schron ◽  
R. G. Knickelbein ◽  
P. S. Aronson ◽  
J. Della Puca ◽  
J. W. Dobbins
Keyword(s):  
Brush Border ◽  
Brush Border Membrane ◽  
Electrical Potential ◽  
Membrane Vesicles ◽  
Disodium Salt ◽  
Brush Border Membrane Vesicles ◽  
Ph Gradient ◽  
Disulfonic Acid ◽  
Rabbit Ileum ◽  
External K

In brush-border membrane vesicles from rabbit ileum, we previously reported pH gradient-stimulated SO4 uptake and presented evidence that this represents carrier-mediated SO4-OH exchange. In the present study inhibitors of SO4-OH exchange (H-SO4 cotransport) were shown not to inhibit Na-SO4 cotransport, suggesting that these are two separate carrier-mediated transport mechanisms. While pH gradient-stimulated SO4 uptake was inhibited 87% by 0.1 mM 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid, disodium salt (DIDS) and 79% by 1.0 mM furosemide, Na+-stimulated SO4 uptake was only inhibited 11 and 0%, respectively. K+ (20 mM), Cl (5 mM), and oxalate (0.25 mM) inhibited pH gradient-stimulated SO4 uptake (38-65%) but had no effect on Na+-stimulated SO4 uptake. Finally, at Na+ concentrations (10 mM) significantly less than that required for Na+-stimulated SO4 uptake (60-100 mM), external Na+ inhibited pH gradient-stimulated SO4 uptake, suggesting two independent effects of this cation. SO4 uptake was also inhibited by external K+ both in the presence and absence of a pH gradient. A Dixon plot of the DIDS-sensitive SO4 uptake under pH gradient conditions yielded a straight line, indicating a single site of interaction between external K+ and the SO4-OH carrier (apparent Ki = 7.2 mM). In contrast to the inhibition by external K+, internal K+ stimulated SO4 uptake. This effect was DIDS sensitive and not enhanced by valinomycin, suggesting an interaction of internal K+ with the SO4-OH exchanger independent of a K+-induced electrical potential. SO4 uptake and the effects of K+ were pH modulated with less SO4 uptake and less K+ effect at higher pH.(ABSTRACT TRUNCATED AT 250 WORDS)

Na+-independent transport of bipolar and cationic amino acids across the luminal membrane of the small intestine

1997 ◽  
Vol 272 (4) ◽  
pp. R1060-R1068 ◽  
Author(s):  
B. G. Munck ◽  
L. K. Munck
Keyword(s):  
Amino Acids ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Short Circuit ◽  
Present System ◽  
Rabbit Ileum ◽  
Beta Alanine ◽  
Brown Adipose ◽  
Cationic Amino Acids

The role of sodium in transport of bipolar and cationic amino acids and their interactions were examined in vitro by measuring unidirectional influx across the brush-border membrane of intact rat jejunal and rabbit ileal epithelia. The chloride-dependent and beta-alanine inhibitable B(0,+) present in rabbit ileum was blocked by combining inhibition by beta-alanine with Na(+)- or Cl(-)-free conditions. Under these conditions, lysine influx across the brush-border membrane is Na+ independent. All Na+-independent influx of cationic and bipolar amino acids is by a system b(0,+) equivalent in the brush-border membrane of both species, where a system y+ is not present. System b(0,+) is shown to be a potent exchanger of intracellular leucine for extracellular lysine and of intracellular lysine for extracellular leucine. The model used to explain leucine stimulation of mucosa to serosa lysine transport can explain Na+ dependence of net lysine absorption. On the assumption that b(0,+) in situ, like the transporter induced by retroperitoneal brown adipose tissue in Xenopus laevi oocytes, acts as an obligatory exchanger, this model can also explain the effects of lysine on short-circuit current and net transport of sodium and the effect on transport capacity by preincubation at Na+-free conditions.

scholarly journals Radiation-inactivation analysis of the Na+/bile acid co-transport system from rabbit ileum

1995 ◽  
Vol 306 (1) ◽  
pp. 241-246 ◽  
Author(s):  
W Kramer ◽  
F Girbig ◽  
U Gutjahr ◽  
S Kowalewski
Keyword(s):  
Bile Acid ◽  
Transport System ◽  
Brush Border ◽  
Binding Proteins ◽  
Brush Border Membrane ◽  
High Energy ◽  
Target Size ◽  
Rabbit Ileum ◽  
Radiation Inactivation ◽  
Bile Acid Binding

The functional-unit molecular size of the Na+/bile acid cotransport system and the apparent target size of the bile-acid-binding proteins in brush-border membrane vesicles from rabbit ileum were determined by radiation inactivation with high-energy electrons. The size of the functional transporting unit for Na(+)-dependent taurocholate uptake was determined to 451 +/- 35 kDa, whereas an apparent molecular mass of 434 +/- 39 kDa was measured for the Na(+)-dependent D-glucose transport system. Proteins of 93 kDa and 14 kDa were identified as putative protein components of the ileal Na+/bile acid cotransporter in the rabbit ileum, whereas a protein of 87 kDa may be involved in passive intestinal bile acid uptake. Photoaffinity labelling with 3- and 7-azi-derivatives of taurocholate revealed a target size of 229 +/- 10 kDa for the 93 kDa protein, and 132 +/- 23 kDa for the 14 kDa protein. These findings indicate that the ileal Na+/bile acid co-transport system is in its functional state a protein complex composed of several subunits. The functional molecular sizes for Na(+)-dependent transport activity and the bile-acid-binding proteins suggest that the Na+/bile acid co-transporter from rabbit ileum is a homotetramer (AB)4 composed of four AB subunits, where A represents the integral 93 kDa and B the peripheral 14 kDa brush-border membrane protein.

Resection of rabbit ileum: effect on brush border membrane enzyme markers and lipids

1985 ◽  
Vol 63 (12) ◽  
pp. 1528-1532 ◽  
Author(s):  
M. Keelan ◽  
K. Walker ◽  
A. B. R. Thomson
Keyword(s):  
Fatty Acids ◽  
Total Cholesterol ◽  
Bile Acids ◽  
Chain Length ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Membrane Composition ◽  
Rabbit Ileum ◽  
Ileal Resection ◽  
Distal Small Intestine

Alterations in transport function have been described 6 weeks after surgical resection of 50% of the distal small intestine. Previous studies demonstrated a modest increase in the jejunal uptake of medium chain length fatty acids following resection, while the uptake of many other lipids (cholesterol, bile acids, fatty alcohols, short and long chain length fatty acids) appears to be unaffected. Marked changes in the kinetic constants for the carrier-mediated uptake of four sugars and leucine were observed following resection, but the changes in transport were not associated with changes in the mucosal surface area. This study was undertaken to examine the possible adaptive mechanisms that occur with ileal resection in the rabbit. A 29% increase in the wet weight of jejunal mucosal scrapings and a 53% increase in jejunal brush border membrane (BBM) protein was observed following resection. The jejunal BBM sucrase (S) was unchanged following ileal resection, but alkaline phosphatase (AP) total activities were increased in the resected rabbits. This resulted in a 45% increase in the ratio of AP/S with resection. The lipid composition (total free fatty acids, total bile acids, total cholesterol, total phospholipids, individual phospholipids, and the ratio of total phospholipids/total cholesterol) of BBM was similar in control and resected rabbits. This suggests that quantitative rather than qualitative changes in the membrane composition may be responsible for the transport changes observed in resected animals.

Distinction between chloride-dependent transport systems for taurine and beta-alanine in rabbit ileum

1992 ◽  
Vol 262 (4) ◽  
pp. G609-G615 ◽  
Author(s):  
L. K. Munck ◽  
B. G. Munck
Keyword(s):  
Brush Border ◽  
Brush Border Membrane ◽  
Transport Systems ◽  
Rabbit Ileum ◽  
Beta Alanine ◽  
Intestinal Transporter ◽  
Maximal Activation ◽  
Dependent Transport ◽  
Taurine Uptake ◽  
Kinetics Of

This study describes the influx of taurine and beta-alanine across the brush-border membrane of rabbit distal ileum. The kinetics of JmcTau [concentration at which half-maximal activation occurs (K1/2) = 41 microM and Jmax = 24 nmol.cm-2.h-1] are consistent with the kinetics of taurine uptake by jejunal brush-border vesicles. The taurine carrier differs from the beta-alanine carrier by being insensitive to leucine inhibition and by the jejunoileal variation of influx along the small intestine. The K1/2 for sodium and chloride activation of the beta-alanine carrier (48 and 8 mM, respectively) differ markedly from the values reported for the taurine carrier. In addition, taurine is not transported by the beta-alanine carrier. Thus the study demonstrates that the taurine and beta-alanine carriers are separate entities, and it adds to the imino and the taurine carriers the beta-alanine carrier as a third chloride-dependent intestinal transporter of amino acids.

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