Intestinal glycyl-L-phenylalanine and L-phenylalanine transport in a euryhaline teleost

1991 ◽  
Vol 260 (3) ◽  
pp. R563-R569 ◽  
Author(s):  
S. J. Reshkin ◽  
G. A. Ahearn
Keyword(s):  
Significant Contribution ◽  
Brush Border Membrane ◽  
Membrane Vesicles ◽  
Transport Mechanisms ◽  
Intestinal Brush Border Membrane ◽  
Overshoot Phenomenon ◽  
Independent Process ◽  
Euryhaline Teleost ◽  
Dipeptide Uptake ◽  
Phenylalanine Transport

The transport mechanisms for the dipeptide glycyl-L-phenylalanine (Gly-Phe) and L-phenylalanine (Phe) were characterized in fish intestinal brush-border membrane vesicles (BBMV). Gly-Phe was rapidly hydrolyzed only intravesicularly with almost total hydrolysis occurring even at 10 s. Dipeptide uptake was not stimulated by an inward gradient of Na, K, or H. Phe uptake was stimulated by an inward gradient of either Na or K but displayed an overshoot phenomenon only in the presence of an Na gradient. Kinetic analysis of the effect of substrate concentration on transport rate revealed that transport of both Gly-Phe and Phe occurred by a saturable process conforming to Michaelis-Menten kinetics. The Km for Gly-Phe was 9.8 +/- 3.5 mM, whereas that for Phe in the presence of Na or K, respectively, was 0.74 +/- 0.13 and 1.1 +/- 0.37 mM. Maximum uptake for Gly-Phe and for Phe in the presence of Na and K was 5.1, 0.9, and 0.4 nmol.mg and protein-1.5 s-1, respectively. Gly-Phe and Phe transport displayed different patterns of inhibition by dipeptides and amino acids. These results suggest that Gly-Phe and Phe are transported via different mechanisms, with Gly-Phe being hydrolyzed during a carrier-mediated, cation-independent process and Phe being transferred via a Na+ cotransport process similar to that described in mammals. During conditions of high luminal dipeptide concentrations, the Gly-Phe pathway may make a significant contribution to total Phe uptake.

Transport characteristics of glutamine in human intestinal brush-border membrane vesicles

1989 ◽  
Vol 256 (1) ◽  
pp. G240-G245 ◽  
Author(s):  
H. M. Said ◽  
K. Van Voorhis ◽  
F. K. Ghishan ◽  
N. Abumurad ◽  
W. Nylander ◽  
...  
Keyword(s):  
Brush Border ◽  
Brush Border Membrane ◽  
Membrane Vesicle ◽  
Membrane Vesicles ◽  
Transport Processes ◽  
Intestinal Brush Border Membrane ◽  
Dependent Process ◽  
Carrier Mediated Transport ◽  
Overshoot Phenomenon ◽  
Independent Process

Transport of glutamine (Gln) across the brush-border membrane of the human intestine was examined using the brush-border membrane vesicle (BBMV) technique. Osmolarity and temperature studies indicate that the uptake of Gln by BBMV is mostly the result of transport of the substrate into the intravesicular space. Transport of Gln was Na+ gradient dependent (out greater than in) with a distinct "overshoot" phenomenon. Initial rate of transport of Gln as a function of concentration was saturable both in the presence and absence of a Na+ gradient (out greater than in). Apparent Km of 1.86 and 1.36 mM and Vmax of 1,906 and 637 pmol.mg protein-1 . 7 s-1 were calculated for the Na+-dependent and the Na+-independent transport processes of Gln, respectively. The transport of [3H]Gln (0.58 mM) by the Na+-dependent and the Na+-independent processes was severely inhibited by the addition to the incubation medium of serine, asparagine, and unlabeled Gln. Inducing a relatively negative intravesicular compartment with the use of valinomycin and an outwardly directed K+ gradient or with the use of anions of different lipid permeabilities indicates that Gln transport by the Na+-dependent process is electrogenic in nature. Transport of Gln by the Na+-independent process, however, appeared to be electroneutral in nature. These results demonstrate the existence of two carrier-mediated transport processes for Gln in the human intestinal BBMV, one is Na+ dependent and the other is Na+ independent. Furthermore, the results suggest that Gln transport by the Na+-dependent process probably occurs by a Gln-Na+ cotransport mechanism.

Transport of procainamide via H+/tertiary amine antiport system in rabbit intestinal brush-border membrane

2000 ◽  
Vol 279 (4) ◽  
pp. G799-G805 ◽  
Author(s):  
Toshiya Katsura ◽  
Hiroshi Mizuuchi ◽  
Yukiya Hashimoto ◽  
Ken-Ichi Inui
Keyword(s):  
Tertiary Amine ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Membrane Vesicles ◽  
Tertiary Amines ◽  
Intestinal Brush Border Membrane ◽  
Intestinal Brush Border ◽  
Rabbit Small Intestine ◽  
Overshoot Phenomenon ◽  
Filtration Technique

Transport characteristics of procainamide in the brush-border membrane isolated from rabbit small intestine were studied by a rapid-filtration technique. Procainamide uptake by brush-border membrane vesicles was stimulated by an outward H+ gradient (pHin= 6.0, pHout = 7.5) against a concentration gradient (overshoot phenomenon), and this stimulation was reduced when the H+ gradient was subjected to rapid dissipation by the presence of a protonophore, FCCP. An outward H+gradient-dependent procainamide uptake was not caused by H+diffusion potential. The initial uptake of procainamide was inhibited by other tertiary amines with N-dimethyl or N-diethyl moieties in their structures, such as triethylamine, dimethylaminoethyl chloride, and diphenhydramine, but not by tetraethylammonium and thiamine. Furthermore, procainamide uptake was stimulated by preloading the vesicles with these tertiary amines ( trans-stimulation effect), indicating the existence of a specific transport system for tertiary amines. These findings indicate that procainamide transport in the intestinal brush-border membrane is mediated by the H+/tertiary amine antiport system that recognizes N-dimethyl or N-diethyl moieties in the structures of tertiary amines.

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.

Folate transport by human intestinal brush-border membrane vesicles

1987 ◽  
Vol 252 (2) ◽  
pp. G229-G236 ◽  
Author(s):  
H. M. Said ◽  
F. K. Ghishan ◽  
R. Redha
Keyword(s):  
Brush Border ◽  
Brush Border Membrane ◽  
Membrane Vesicle ◽  
Membrane Vesicles ◽  
Disulfonic Acid ◽  
Folate Transport ◽  
Intestinal Brush Border Membrane ◽  
Transport Carrier ◽  
Incubation Buffer

Transport of folic acid (Pte-Glu) across the brush-border membrane of human intestine was studied using brush-border membrane vesicle (BBMV) technique. The transport of Pte-Glu was higher in BBMV prepared from the jejunum than those prepared from the ileum (0.70 +/- 0.05 and 0.14 +/- 0.02 pmol X mg protein-1 X 10 s-1, respectively). The transport of Pte-Glu appeared to be carrier mediated and was pH dependent and increased with decreasing incubation buffer pH; saturable (Kt = 1.69 microM, Vmax = 4.72 pmol X mg protein-1 X 10 s-1); inhibited in a competitive manner by the structural analogues 5-methyltetrahydrofolate, methotrexate, and 5-formyltetrahydrofolate (Ki = 2.2, 1.4 and 1.4 microM, respectively); not affected by inducing a relatively positive or negative intravesicular compartment; independent of Na+ gradient; and inhibited by 4,4'-diisothiocyanatostlibene-2,2'-disulfonic acid (DIDS), an anion exchange inhibitor. The increase in Pte-Glu transport on decreasing incubation buffer pH appeared to be in part mediated through a direct effect of acidic pH on the transport carrier and in part through the pH gradient imposed by activating Pte-Glu-:OH- exchange and/or Pte-Glu-:H+ co-transport mechanisms. The important role of an acidic extravesicular environment in Pte-Glu transport is consistent with a role for the intestinal surface acid microclimate in folate transport. These results demonstrate that Pte-Glu transport in human BBMV occurs by a carrier-mediated system that is similar to that described for rat and rabbit intestinal BBMV.

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).

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