The mechanism of Na+-l-lactate cotransport by brush border membrane vesicles from horse kidney: Analysis of rapid equilibrium kinetics in absence of membrane potential

1983 ◽  
Vol 71 (3) ◽  
pp. 163-171 ◽  
Author(s):  
Raymond Mengual ◽  
Pierre Sudaka
Keyword(s):  
Membrane Potential ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Membrane Vesicles ◽  
Brush Border Membrane Vesicles ◽  
Rapid Equilibrium

Nicotinic acid transport by brush border membrane vesicles from rabbit kidney

1981 ◽  
Vol 240 (3) ◽  
pp. F185-F191 ◽  
Author(s):  
E. F. Boumendil-Podevin ◽  
R. A. Podevin
Keyword(s):  
Membrane Potential ◽  
Nicotinic Acid ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Isonicotinic Acid ◽  
Membrane Vesicles ◽  
Brush Border Membrane Vesicles ◽  
Rabbit Kidney ◽  
Internal Space ◽  
Acid Uptake

The transport of nicotinic acid was investigated in brush border membrane vesicles isolated from rabbit kidney. The imposition of a Na+ gradient (out to in) induced a transient stimulation of nicotinic acid uptake above its final equilibrium value. This stimulation was specific for Na+. The uptake of nicotinic acid by the brush border membranes represented transport into an internal space and occurred in the absence of significant nicotinic acid degradation. The Na+ gradient-dependent uptake of nicotinic acid was saturable, apparent Km = 0.3 mM. Uptake of nicotinic acid was inhibited by its two isomers: picolinic and isonicotinic acid. In contrast, pyridine derivatives with two carboxyl groups or an amide group in addition to the carboxyl group were without inhibitory effect. Evaluation of changes in membrane potential using the lipophilic cation triphenylmethylphosphonium demonstrated that conditions that transiently generated either an interior-positive or an interior-negative membrane potential failed to affect the Na+-dependent transport of nicotinic acid. These findings provide evidence of the existence on the luminal membrane of a Na+ gradient-dependent and electroneutral transport system for nicotinic acid.

Ca2+ transport pathways in brush-border membrane vesicles of crustacean antennal glands

1993 ◽  
Vol 264 (6) ◽  
pp. R1206-R1213 ◽  
Author(s):  
G. A. Ahearn ◽  
P. Franco
Keyword(s):  
Membrane Potential ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Membrane Vesicles ◽  
Brush Border Membrane Vesicles ◽  
Carrier System ◽  
Transport Pathways ◽  
45Ca Uptake ◽  
Negative Membrane Potential ◽  
Antennal Glands

Calcium uptake by brush-border membrane vesicles of Atlantic lobster (Homarus americanus) kidneys (antennal glands) in independent experiments was stimulated by outwardly directed Na or H gradients. In the absence of external amiloride, 45Ca uptake was strongly stimulated by an outwardly directed Na gradient, and this stimulation was enhanced by the addition of an inside-negative membrane potential. External amiloride (2 mM) reduced 45Ca uptake sixfold and lowered sensitivity to membrane potential. 45Ca influx kinetics (2.5-s uptake) in the presence of an outwardly directed H gradient and inside-negative membrane potential were composed of three components: 1) an amiloride-sensitive carrier system, 2) an amiloride-insensitive carrier system, and 3) a verapamil- and membrane potential-sensitive process that may represent diffusional transfer through a calcium channel. It was concluded that 45Ca entry by the amiloride-sensitive process occurred by a previously described electrogenic 2 Na-1 H antiport mechanism [Ahearn, G., and L. Clay. Am. J. Physiol. 257 (Regulatory Integrative Comp. Physiol. 26): R484-R493, 1989; Am. J. Physiol. 259 (Renal Fluid Electrolyte Physiol. 28): F758-F767, 1990; Ahearn, G., P. Franco, and L. Clay. J. Membr. Biol. 116: 215-226, 1990]. 45Ca influx by the amiloride-insensitive mechanism occurred by an apparent electroneutral 1 Ca-2 Na exchange. Transport stoichiometry of the latter mechanism was tentatively established by experiments determining intravesicular Na binding properties and by its apparent lack of response to a membrane potential. At physiological Na, Ca, and H concentrations in the antennal gland lumen and epithelial cytosol, these three calcium transport pathways individually may make significant contributions to net calcium reabsorption to the blood.

Ionic permeabilities of rat renal cortical brush-border membrane vesicles

1987 ◽  
Vol 252 (4) ◽  
pp. F700-F711
Author(s):  
M. S. Lipkowitz ◽  
R. G. Abramson
Keyword(s):  
Membrane Potential ◽  
Glucose Uptake ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Electrolyte Concentration ◽  
Membrane Vesicles ◽  
Brush Border Membrane Vesicles ◽  
Prolonged Incubation ◽  
New Methods ◽  
Electrochemical Equilibrium

It is generally assumed that electrolytes equilibrate readily across renal cortical brush-border membrane vesicles (BBMV). This assumption was tested by use of two new methods in rat BBMV prepared with free-flow electrophoresis (FFE), Mg aggregation, or Ca aggregation. Intravesicular KCl and RbCl concentrations, as well as the conductance of Cl relative to K (GCl/GK) and GNa/GK were determined with the fluorescent, potential-sensitive probe 3,3'-dipropylthiadicarbocyanine iodide [diS-C3-(5)]; intravesicular KCl concentration was also approximated utilizing the response of Na-dependent [3H]glucose uptake to variations in the membrane potential. These studies demonstrated that KCl fails to attain electrochemical equilibrium in BBMV prepared by the three methods, despite prolonged incubation at 22 degrees C; a significant, inwardly directed electrolyte gradient was sustained in all cases. The intravesicular electrolyte concentration was lower in BBMV prepared with FFE than in those prepared with Mg or Ca. GCl/GK was lowest in BBMV prepared with FFE and highest in those prepared with Ca; GNa/GK was comparable in all preparations. The apparent impermeance of BBMV may impact significantly in interpreting data from studies that require knowledge of the precise concentration of intravesicular electrolytes.

Facilitated diffusion of urate in avian brush-border membrane vesicles

2002 ◽  
Vol 283 (4) ◽  
pp. C1155-C1162 ◽  
Author(s):  
Steven M. Grassl
Keyword(s):  
Membrane Potential ◽  
Proximal Tubule ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Membrane Vesicles ◽  
Brush Border Membrane Vesicles ◽  
Facilitated Diffusion ◽  
Transport Pathways ◽  
Proximal Tubule Cells ◽  
Avian Kidney

Membrane transport pathways mediating transcellular secretion of urate across the proximal tubule were investigated in brush-border membrane vesicles (BBMV) isolated from avian kidney. An inside-positive K diffusion potential induced a conductive uptake of urate to levels exceeding equilibrium. Protonophore-induced dissipation of membrane potential significantly reduced voltage-driven urate uptake. Conductive uptake of urate was inhibitor sensitive, substrate specific, and a saturable function of urate concentration. Urate uptake was trans-stimulated by urate and cis-inhibited by p-aminohippurate (PAH). Conductive uptake of PAH was cis-inhibited by urate. Urate uptake was unaffected by an outward α-ketoglutarate gradient. In the absence of a membrane potential, urate uptake was similar in the presence and absence of an imposed inside-alkaline pH gradient or an outward Cl gradient. These observations suggest a uniporter-mediated facilitated diffusion of urate as a pathway for passive efflux across the brush border membrane of urate-secreting proximal tubule cells.

scholarly journals The Escherichia coli Enterotoxin STb Permeabilizes Piglet Jejunal Brush Border Membrane Vesicles

2007 ◽  
Vol 75 (5) ◽  
pp. 2208-2213 ◽  
Author(s):  
Carina Gonçalves ◽  
Vincent Vachon ◽  
Jean-Louis Schwartz ◽  
J. Daniel Dubreuil
Keyword(s):  
Escherichia Coli ◽  
Membrane Potential ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Membrane Vesicles ◽  
Brush Border Membrane Vesicles ◽  
Ionic Selectivity ◽  
Intact Membrane ◽  
Target Membrane ◽  
First Time

ABSTRACT The membrane-permeabilizing ability of the Escherichia coli enterotoxin STb was evaluated using brush border membrane vesicles isolated from piglet jejunum and a membrane-potential-sensitive fluorescent probe, 3,3′-dipropylthiadicarbocyanine iodide. A strong membrane potential was generated by the efflux of K+ ions from the vesicles in the presence of the potassium ionophore valinomycin. Under these conditions, preincubation of the vesicles with STb efficiently depolarized the membrane in a dose-dependent and saturable manner. This activity was independent of pH, however, at least between pH 5.5 and 8.0. On the other hand, in the absence of valinomycin, STb had no significant influence on the measured fluorescence levels, indicating that it was unable to modify the ionic selectivity of the intact membrane. In agreement with the fact that the integrity of the disulfide bridges of STb is known to be essential for its biological activity, a reduced and alkylated form of the toxin was unable to depolarize the membrane in the presence of valinomycin. Furthermore, two previously described poorly active STb mutants, M42S and K22A-K23A, showed no membrane-permeabilizing capacity. These results demonstrate for the first time that STb can permeabilize its target membrane and suggest that it does so by forming nonspecific pores.

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.

scholarly journals Membrane-Potential-Sensitive, Na+-Independent Lysine Transport by Lobster Hepatopancreatic Brush Border Membrane Vesicles

1987 ◽  
Vol 127 (1) ◽  
pp. 373-387
Author(s):  
GREGORY A. AHEARN ◽  
LAUREL P. CLAY
Keyword(s):  
Membrane Potential ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Membrane Vesicles ◽  
Brush Border Membrane Vesicles ◽  
Acidic Ph ◽  
S Uptake ◽  
Apparent Diffusion ◽  
Leucine Transport ◽  
Dependent Transport

Transport of l-[3H]lysine by epithelial brush border membrane vesicles (BBMV) of lobster hepatopancreas, formed by a magnesium precipitation technique, was insensitive to transmembrane gradients of Na+, K+, TMA+ or H+. Apparent initial lysine entry rates (15 s uptake) and extent of amino acid accumulation against a concentration gradient (overshoot) were both stimulated by transmembrane anion gradients according to the following sequence: SCN− > Cl− > gluconate−. The magnitude of this anion-gradient-dependent transport was significantly increased by bilateral acidic pH. Lysine transport at acidic pH strongly responded to transmembrane potential developed by addition of valinomycin to K+-loaded vesicles, or was markedly reduced if K+-equilibrated vesicles were incubated with the ionophore in the presence of an inwardly directed SCN− gradient. Lysine influx occurred by the combination of at least one carrier process and ‘apparent diffusion’. l-Arginine, l-alanine and l-leucine, added to the external medium, were all strong inhibitors of lysine influx. The first two were competitive inhibitors of lysine entry, while the latter was non-competitive in effect. These results suggest that lysine, arginine and alanine may share a common, Na+-independent, membrane-potential-sensitive transport mechanism in lobster BBMV. Leucine transport may occur in these membranes by a separate agency.

Na+-H+ exchange in rat colonic brush-border membrane vesicles

1986 ◽  
Vol 250 (6) ◽  
pp. G781-G787
Author(s):  
E. S. Foster ◽  
P. K. Dudeja ◽  
T. A. Brasitus
Keyword(s):  
Membrane Potential ◽  
Acridine Orange ◽  
Large Intestine ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Exchange Process ◽  
Membrane Vesicles ◽  
Brush Border Membrane Vesicles ◽  
Proton Efflux ◽  
Ph Gradients

To demonstrate the presence of a Na+-H+ exchange process in brush-border membrane vesicles from rat colonocytes, the fluorescence response of acridine orange was used to monitor the formation and dissipation of pH gradients. An inwardly directed Na+ gradient stimulated the outward flux of H+, whereas proton influx was stimulated by an outwardly directed Na+ gradient. Since the ionophore valinomycin in the presence of a K+ gradient did not alter Na+-stimulated proton efflux, the interrelationship of Na+ and H+ movement could not be explained solely on the basis of a membrane potential. Na+-stimulated proton efflux was saturable with a Km for Na+ of 20.1 +/- 1.6 mM. Inwardly directed Li+ gradients also stimulated proton efflux, and the Km for Li+ was 30.2 +/- 1.7 mM. In contrast, impermeant cations failed to stimulate the outward flux of H+. Amiloride (1 mM) inhibited both Na+-stimulated proton efflux and influx. Therefore, Na+-H+ exchange is present in rat colonic brush-border membranes and has characteristics similar to other Na+-H+ antiporters. This exchange process may be an important mechanism for Na+ absorption in the large intestine.

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