scholarly journals Transport of amino acids (l‐valine, l‐lysine, l‐glutamic acid) and sucrose into plasma membrane vesicles isolated from cotyledons of developing pea seeds

2000 ◽  
Vol 51 (351) ◽  
pp. 1663-1670 ◽  
Author(s):  
A. de Jong ◽  
A.C. Borstlap
Keyword(s):  
Amino Acids ◽  
Plasma Membrane ◽  
Glutamic Acid ◽  
Membrane Vesicles ◽  
Plasma Membrane Vesicles ◽  
Pea Seeds

Anionic amino acid transport systems in isolated basal plasma membrane of human placenta

1990 ◽  
Vol 259 (1) ◽  
pp. C47-C55 ◽  
Author(s):  
S. D. Hoeltzli ◽  
L. K. Kelley ◽  
A. J. Moe ◽  
C. H. Smith
Keyword(s):  
Amino Acids ◽  
Plasma Membrane ◽  
Membrane Vesicles ◽  
Transport Systems ◽  
Acid Transport ◽  
Plasma Membrane Vesicles ◽  
Basal Plasma Membrane ◽  
Sodium Dependent ◽  
Basal Plasma ◽  
Potassium Gradient

The placenta absorbs anionic amino acids from the maternal and fetal circulations but does not significantly transfer these amino acids from mother to fetus. Uptake of L-aspartate and L-glutamate by basal (fetal-facing) plasma membrane vesicles from placental syncytiotrophoblast was stimulated by an inward sodium and an outward potassium gradient. Measurable saturable uptake was entirely sodium dependent and electrogenic. Studies of concentration dependence resolved a high-affinity (microM) system that has characteristics of the X-AG system found in other tissues including the placental microvillous plasma membrane. Uptake of 0.2 microM L-glutamate was inhibited by 2 mM L-glutamate, L-aspartate, D-aspartate, L-cysteate, and L-cysteinesulfinic acid and was uninhibited by 2 mM D-glutamate, L-glutamine, L-alanine, L-serine, L-asparagine, and taurine or by 1 mM methylaminoisobutyric acid. The X-AG system in the two membranes of the placental syncytiotrophoblast may mediate the concentrative uptake of anionic amino acids from the maternal and fetal circulations into the placenta.

Kinetic and energetic aspects of the inhibition of taurocholate uptake by Na+-dependent amino acids: studies in rat liver plasma membrane vesicles

1985 ◽  
Vol 249 (1) ◽  
pp. G120-G124
Author(s):  
B. L. Blitzer ◽  
R. L. Bueler
Keyword(s):  
Amino Acids ◽  
Plasma Membrane ◽  
Bile Acid ◽  
Amino Acid ◽  
Initial Velocity ◽  
Membrane Vesicles ◽  
Acid Uptake ◽  
Plasma Membrane Vesicles ◽  
Liver Plasma Membrane ◽  
Bile Acid Uptake

The kinetic and energetic aspects of the inhibition of taurocholate uptake by the Na+-dependent amino acid L-alanine were studied in rat basolateral liver plasma membrane vesicles. In the presence of an inwardly directed Na+ gradient, alanine (5 mM) reduced the initial velocity of taurocholate uptake to 60% of control and virtually abolished the overshoot. In the presence of a K+ gradient, the slow rate of Na+-independent taurocholate uptake was similar in the presence or absence of the amino acid. Inhibition of Na+-dependent taurocholate uptake increased nonlinearly with alanine concentration (half-maximal inhibition at approximately 1 mM) and plateaued at 5–10 mM. Kinetic studies showed that alanine significantly reduced the Vmax for taurocholate uptake from 6.32 +/- 0.22 to 3.68 +/- 0.21 nmol X mg prot-1 X min-1 but did not significantly affect taurocholate Km (38.4 +/- 3.6 vs. 29.0 +/- 4.9 microM). In contrast, the Na+-independent amino acid 2-aminobicyclo[2.2.1]heptane-2-carboxylic acid did not affect either the initial velocity or peak uptake of taurocholate. The effects of alanine on the driving forces for bile acid uptake were directly assessed by measuring vesicle uptake of 22Na. At early time points, 22Na uptake was faster in the presence of alanine than under control conditions. These findings provide further evidence that Na+-dependent amino acids noncompetitively inhibit Na+-dependent bile acid uptake in association with accelerated dissipation of the transmembrane Na+ gradient and extend previous observations of this phenomenon made in isolated rat hepatocytes [Am. J. Physiol. 245 (Gastrointest. Liver Physiol. 8): G399-G403, 1983].

Transport in isolated plasma membranes

1978 ◽  
Vol 234 (2) ◽  
pp. F89-F96 ◽  
Author(s):  
U. Hopfer
Keyword(s):  
Amino Acids ◽  
Plasma Membrane ◽  
Concentration Gradient ◽  
Plasma Membranes ◽  
Experimental System ◽  
Membrane Vesicles ◽  
Plasma Membrane Vesicles ◽  
Major Function ◽  
Transport Studies ◽  
Major Disadvantage

Plasma membrane vesicles constitute a simpler experimental system for studying transport compared to cells or intact tissue. The principal advantages of the vesicle approach are the elimination of metabolism as a complicating factor and the ability to control the composition of the solutions on both sides of the membrane. The major disadvantage is vesicle heterogeneity. However, techniques are available to avoid the kinetic artifacts that are due to the heterogeneity. Results of transport studies using membrane vesicles have conclusively shown that D-glucose and amino acids are co-transported with Na+ and that transport against a concentration gradient is driven by an electrochemical Na+ gradient. As a result of coupling between Na+ and the nonelectrolytes, estimates of the kinetic parameters of transport, Km and Vmax, require that the load on the Na+ gradient be taken into account. This has rarely been done. Although electrolyte transport is a major function of the plasma membrane, knowledge of the mechanisms involved is limited. Future investigations employing specific ionophores should contribute much to our understanding of the mechanisms underlying ATP-independent ion transport. Examples of the application of membrane vesicles for studying transport-related aspects of diseases are discussed.

Fasting enhances taurine transport by rat liver plasma membrane vesicles

1994 ◽  
Vol 267 (5) ◽  
pp. G932-G937
Author(s):  
D. Berkowitz ◽  
P. Hug ◽  
R. G. Sleight ◽  
J. C. Bucuvalas
Keyword(s):  
Amino Acids ◽  
Plasma Membrane ◽  
Membrane Vesicles ◽  
Male Rats ◽  
Control Group ◽  
Plasma Membrane Vesicles ◽  
Hepatic Transport ◽  
Taurine Transport ◽  
Liver Plasma Membrane ◽  
Taurine Uptake

Hepatic taurine stores are maintained by biosynthesis from the sulfur-containing amino acids, methionine and cysteine, and by uptake via a Na(+)- and Cl(-)-dependent transport system, which is specific for beta-amino acids. We hypothesized that liver stores of taurine are maintained by enhanced hepatic transport during fasting when dietary sources for taurine and its precursors are diminished. Liver plasma membrane vesicles, enriched for the basolateral domain, were prepared from adult male rats fasted for 72 h and from control rats. The maximum velocity for Na(+)-dependent taurine uptake was twofold greater for the fasted group compared with the control group (0.87 +/- 0.09 vs. 0.31 +/- 0.03 nmol.mg protein-1.min-1). The apparent Michaelis constant for taurine was also greater for fasted compared with control (154.0 +/- 0.5 vs. 80.0 +/- 2.0 microM). gamma-Aminobutyric acid, but not alanine or glutamine, abolished the effect of fasting on hepatic taurine transport. To determine the effect of fasting independent of changes in the lipid microenvironment, taurine uptake was measured in proteoliposomes reconstituted by inserting detergent-solubilized membrane proteins into asolectin vesicles. Taurine uptake by proteoliposomes reconstituted from membranes prepared from the fasted group was significantly greater than from the control group. We conclude that Na(+)-dependent taurine transport is enhanced in liver plasma membranes prepared from fasted rats. Our findings imply that enhanced taurine uptake with fasting is due to either an increased number of functional carriers or activation of existing transporters.

Activation by intravesicular amino acids of system L-mediated serine uptake into human placental microvillous plasma membrane vesicles

Placenta ◽  
2014 ◽  
Vol 35 (9) ◽  
pp. A99
Author(s):  
Kate Widdows ◽  
Nont Panitchob ◽  
Emma Lofthouse ◽  
Ian Crocker ◽  
Colin Sibley ◽  
...  
Keyword(s):  
Amino Acids ◽  
Plasma Membrane ◽  
Membrane Vesicles ◽  
Plasma Membrane Vesicles ◽  
System L
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