Characteristics of glutamine transport in dog jejunal brush-border membrane vesicles

1989 ◽  
Vol 257 (1) ◽  
pp. G80-G85 ◽  
Author(s):  
N. M. Bulus ◽  
N. N. Abumrad ◽  
F. K. Ghishan
Keyword(s):  
Brush Border ◽  
Brush Border Membrane ◽  
Ph Dependence ◽  
Membrane Vesicles ◽  
Brush Border Membrane Vesicles ◽  
Transport Systems ◽  
System A ◽  
System L ◽  
Glutamine Transport ◽  
Glutamine Uptake

The present study characterizes glutamine transport across brush-border membrane vesicles (BBMV) prepared from dog jejunum. The purity of these vesicles was demonstrated by a 20-fold enrichment of leucine aminopeptidase, a marker for BBM. Glutamine uptake was found to occur into an osmotically active space with no membrane binding and to exhibit temperature and pH dependence (optimal uptake at pH 7-7.5). Glutamine uptake was driven by an inwardly directed Na+ gradient with a distinct overshoot not observed under K+ gradient. Lithium could not substitute for Na+ as a stimulator of glutamine uptake. Na+-dependent glutamine uptake was not inhibited by methylaminoisobutyric acid, a typical substrate for system A, and was found to be electrogenic and saturable with a Km of 0.97 +/- 0.58 mM and a Vmax of 3.93 +/- 0.99 nmol.mg protein-1.10 s-1. A Na+-glutamine coupling ratio of 1:1 could be demonstrated by a plot of Hill transformation. Na+-independent glutamine uptake was found to be electroneutral and saturable with a Km of 3.70 +/- 0.66 mM and a Vmax of 2.70 +/- 1.55 nmol.mg protein-1.10 s-1. Inhibition studies confirmed the presence of a Na+-dependent as well as a Na+-independent carrier for glutamine uptake. We conclude that glutamine uptake across dog BBMV occurs via two transport systems: a Na+-dependent high-affinity system similar to the neutral brush-border system and a Na+-independent lower-affinity system similar to system L.

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.

Potential-dependent D-glucose uptake by renal brush border membrane vesicles in the absence of sodium

1982 ◽  
Vol 242 (4) ◽  
pp. F340-F345
Author(s):  
S. Hilden ◽  
B. Sacktor
Keyword(s):  
Membrane Potential ◽  
Glucose Uptake ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Membrane Vesicles ◽  
Brush Border Membrane Vesicles ◽  
Transport Systems ◽  
Uptake System ◽  
Renal Brush Border Membrane ◽  
Renal Brush Border

The uptake of D-glucose by renal brush border membrane vesicles was studied in the absence of Na+. Uptake of the sugar was membrane potential dependent (inside negative), inhibited by phlorizin, sugar and stereospecific, accelerated by exchange diffusion, saturable, and temperature dependent. The binding of phlorizin in the absence of Na+ was also increased by a membrane potential (inside negative). Thus, the properties of this membrane potential-dependent, Na+-independent sugar transport system resembled those described for the Na+-D-glucose cotransport system. In the absence of Na+ but in the presence of a valinomycin-induced K+ diffusion potential the apparent Km for D-glucose was 43 mM. This contrasted with an apparent Km of 1.8 mM for the Na+ chemical gradient system. Therefore, the Na+-independent uptake system represented a low-affinity transport mechanism. It is suggested that the same carrier mediated the Na+-independent and Na+-dependent transport systems. A hypothetical model for the membrane potential-dependent stimulation of D-glucose uptake in the absence of Na+ is proposed.

Multiple transport systems for organic cations in renal brush-border membrane vesicles

1989 ◽  
Vol 256 (4) ◽  
pp. F540-F548 ◽  
Author(s):  
Y. Miyamoto ◽  
C. Tiruppathi ◽  
V. Ganapathy ◽  
F. H. Leibach
Keyword(s):  
Brush Border ◽  
Brush Border Membrane ◽  
Membrane Vesicles ◽  
Brush Border Membrane Vesicles ◽  
Diffusion Potential ◽  
Transport Systems ◽  
Organic Cations ◽  
Uptake Kinetic ◽  
Carrier Systems ◽  
Renal Brush Border

The characteristics of guanidine uptake in brush-border membrane vesicles isolated from rabbit renal cortex were investigated. Guanidine uptake was markedly stimulated by an outwardly directed H+ gradient, resulting in a transient uphill transport. This stimulation was not due to an inside-negative, H+-diffusion potential because an ionophore-induced H+-diffusion potential and a K+-diffusion potential (both inside-negative) failed to enhance guanidine uptake. The H+ gradient itself appeared to be the driving force for the uptake. These data suggest that guanidine-H+ antiport (or guanidine-OH- symport) is the mechanism of guanidine uptake in these membrane vesicles. Guanidine uptake was only minimally inhibited by organic cations such as tetraethylammonium, N1-methylnicotinamide, and choline, but many other organic cations such as amiloride, clonidine, imipramine, and harmaline caused considerable inhibition. Uptake of radiolabeled guanidine was inhibited more effectively by guanidine than by tetraethylammonium, whereas uptake of radiolabeled tetraethylammonium was inhibited more effectively by tetraethylammonium than by guanidine. beta-Lactam antibiotics did not inhibit guanidine uptake but did inhibit tetraethylammonium uptake. Kinetic analysis showed that there were at least two kinetically distinct carrier systems for guanidine uptake, whereas tetraethylammonium uptake occurred via a single carrier system. These data provide evidence that renal brush-border membranes possess multiple carrier systems for organic cations.

Sulphate and phosphate transport in the renal proximal tubule

1982 ◽  
Vol 299 (1097) ◽  
pp. 549-558 ◽  
Keyword(s):  
Cell Membrane ◽  
Proximal Tubule ◽  
Brush Border ◽  
Inorganic Phosphate ◽  
Brush Border Membrane ◽  
Ph Dependence ◽  
Membrane Vesicles ◽  
Dicarboxylic Acids ◽  
Phosphate Transport ◽  
Brush Border Membrane Vesicles

Experiments performed on microperfused proximal tubules and brush-border membrane vesicles revealed that inorganic phosphate is actively reabsorbed in the proximal tubule involving a 2 Na + -HPO 2- 4 or H 2 PO 4 - co-transport step in the brush-border membrane and a sodium-independent exit step in the basolateral cell membrane. Na + - phosphate co-transport is competitively inhibited by arsenate. The transtubular transport regulation is mirrored by the brush-border transport step: it is inhibited by parathyroid hormone intracellularly mediated by cyclic AMP. Transepithelial inorganic phosphate (P i ) transport and Na + -dependent P i transport across the brush-border membrane correlates inversely with the P i content of the diet. Intraluminal acidification as well as intracellular alkalinization led to a reduction of transepithelial P i transport. Data from brush-border membrane vesicles indicate that high luminal H + concentrations reduce the affinity for Na + of the Na + -phosphate co-transport system, and that this mechanism might be responsible for the pH dependence of phosphate reabsorption. Contraluminal influx of P i from the interstitium into the cell could be partly inhibited by 4,4'-diisothiocyanostilbene-2,2'-disulphonic acid (DIDS). It is not, however, changed when dicarboxylic acids are present or when the pH of the perfusate is reduced to pH 6. Sulphate is actively reabsorbed, involving electroneutral 2 Na + -SO 2 - 4 co-transport through the brush-border membrane. This transport step is inhibited by thiosulphate and molybdate, but not by phosphate or tungstate. The transtubular active sulphate reabsorption is not pH dependent, but is diminished by the absence of bicarbonate. The transport of sulphate through the contraluminal cell side is inhibited by DIDS and diminished when the capillary perfusate contains no bicarbonate or chloride. The latter data indicate the presence of an anion exchange system in the contraluminal cell membrane like that in the erythrocyte membrane.

scholarly journals Maturational Changes in Glutamine Transport by Rat Jejunal Brush Border Membrane Vesicles

1990 ◽  
Vol 27 (5) ◽  
pp. 519-524 ◽  
Author(s):  
Fadheela T Al-Mahroos ◽  
Nada Bulus ◽  
Naji Abumrad ◽  
Hamid Said ◽  
Fayez K Ghishan
Keyword(s):  
Brush Border ◽  
Brush Border Membrane ◽  
Membrane Vesicles ◽  
Brush Border Membrane Vesicles ◽  
Glutamine Transport

Age-related changes in sodium-dependent glucose transport in rat small intestine

1986 ◽  
Vol 251 (2) ◽  
pp. G208-G217 ◽  
Author(s):  
H. J. Freeman ◽  
G. A. Quamme
Keyword(s):  
Small Intestine ◽  
Glucose Transport ◽  
Brush Border ◽  
Brush Border Membrane ◽  
High Capacity ◽  
Membrane Vesicles ◽  
Distal Segment ◽  
Brush Border Membrane Vesicles ◽  
Transport Systems ◽  
Sodium Dependent

Brush-border membrane vesicles were purified from jejunoileal segments of rats ranging from 3 to 156 wk. The kinetics of sodium-dependent glucose cotransport were studied under voltage-clamped, zero trans conditions over a wide range of cis-glucose concentrations (0.005-1.5 mM). Initial glucose uptake in brush-border membrane vesicles isolated from the proximal intestinal segment (50 cm from ligament of Treitz) of rats less than 7-8 wk of age demonstrated a distinct curvilinear Hofstee plot consistent with multiple-transport mechanisms. One system possessed an apparent Vmax of 10.6 +/- 0.5 nmol X mg prot-1 X min-1 and Km of 630 +/- 18 microM. The second system was characterized by Vmax of 0.9 +/- 0.1 nmol X mg prot-1 X min-1 and Km of 12 +/- 1 microM. In contrast, the distal segment (50 cm to end of small intestine) possessed only one sodium-dependent glucose carrier system. The apparent Vmax and Km were 1.11 +/- 0.20 nmol X mg protein-1 X min-1 and 49 +/- 7 microM, respectively. Sodium-activation curves in the presence of 0.3 and 0.03 mM glucose were consistent with more than one sodium ion with both systems. In contrast, rats 12-13 wk old and older possessed both sodium-dependent transport systems in the proximal early and distal small intestine. The high-capacity system is more abundant in the proximal than the distal segment. These data suggest that, under these specific conditions, there are two sodium-dependent glucose carriers in the intestine of young rats: one located in the jejunum characterized by high capacity and low affinity, and the second located throughout the jejunoileum characterized by low capacity and high affinity. Furthermore with age there is a development of the low-affinity system in the distal segments so that both systems are found along the length of the jejunum and ileum. Accordingly, serial and parallel heterogeneity of sodium-dependent glucose transport exists along the small intestine.

scholarly journals Heterogeneity of l-alanine transport systems in brush-border membrane vesicles from rat placenta during late gestation

1992 ◽  
Vol 288 (1) ◽  
pp. 47-53 ◽  
Author(s):  
S R Alonso-Torre ◽  
M A Serrano ◽  
J M Medina ◽  
F Alvarado
Keyword(s):  
Alkali Metal ◽  
Metal Ions ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Linear Regression Analysis ◽  
Membrane Vesicles ◽  
Brush Border Membrane Vesicles ◽  
Transport Systems ◽  
Alkali Metal Ions ◽  
Alanine Transport

The placental uptake of L-alanine was studied by using purified brush-border membrane vesicles from rat trophoblasts. Saturation curves were carried out at 37 degrees C in buffers containing 100 mM (zero-trans)-NaSCN, -NaCl, -KSCN, -KCl, or -N-methyl-D-glucamine gluconate. The uncorrected uptake results were fitted by non-linear regression analysis to an equation involving one diffusional component either one or two saturable Michaelian transport terms. In the presence of NaCl, two distinct L-alanine transport systems were distinguished, named respectively System 1 (S-1; Vm1 about 760 pmol/s per mg of protein; KT1 = 0.5 mM) and System 2 (S-2; Vm2 about 1700 pmol/s per mg; KT2 = 9 mM). In contrast, in the presence of K+ (KCl = KSCN) or in the absence of any alkali-metal ions (N-methyl-D-glucamine gluconate), only one saturable system was apparent, which we identify as S-2. When Na+ is present, S-1, but not S-2, appears to be rheogenic, since its maximal transport capacity significantly increases in the presence of an inside-negative membrane potential, created either by replacing Cl- with the permeant anion thiocyanate (NaSCN > NaCl) or by applying an appropriate K+ gradient and valinomycin. alpha-(Methylamino)isobutyrate (methyl-AIB) appears to be a substrate of S-1, but not of S-2. For reasons that remain to be explained, however, methyl-AIB inhibits S-2. We conclude that S-1 represents a truly Na(+)-dependent mechanism, where Na+ behaves as an obligatory activator, whereas S-2 cannot discriminate between Na+ and K+, although its activity is higher in the presence of alkali-metal ions than in their absence (Na+ = K+ > N-methyl-D-glucammonium ion). S-2 appears to be fully developed 2 days before birth, whereas S-1 undergoes a capacity-type activation between days 19.5 and 21.5 of gestation, i.e. its apparent Vmax. nearly doubles, whereas its KT remains constant.

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