scholarly journals Sodium-dependent alanine transport in plasma-membrane vesicles from rat liver

1978 ◽  
Vol 174 (3) ◽  
pp. 1083-1086 ◽  
Author(s):  
J M M van Amelsvoort ◽  
H J Sips ◽  
K van Dam
Keyword(s):  
Plasma Membrane ◽  
Rat Liver ◽  
Membrane Vesicles ◽  
Plasma Membrane Vesicles ◽  
Alanine Transport ◽  
Carbonyl Cyanide ◽  
Sodium Dependent

L-Alanine transport was studied in plasma-membrane vesicles from rat liver. A gradient of NaSCN, but not of KSCN, stimulated alanine uptake. Monensin plus carbonyl cyanide p-trifluoromethoxyphenylhydrazone abolished the observed overshoot in uptake. After equilibration of alanine, NaSCN induced uphill transport.

Diabetes enhances activity of alanine transport in liver plasma membrane vesicles

1985 ◽  
Vol 248 (5) ◽  
pp. E581-E587 ◽  
Author(s):  
N. R. Rosenthal ◽  
R. Jacob ◽  
E. Barrett
Keyword(s):  
Plasma Membrane ◽  
Membrane Vesicles ◽  
Diabetic Rats ◽  
Control Group ◽  
Similar Degree ◽  
Plasma Membrane Vesicles ◽  
Fourfold Increase ◽  
Alanine Transport ◽  
Sodium Dependent ◽  
22Na Uptake

In the present study plasma membrane vesicles were prepared from livers of control and alloxan-induced diabetic rats and the substrate specificity and kinetic characteristics of alanine transport determined in both groups. Sodium-dependent alanine uptake at physiological alanine concentrations (100 microM) was enhanced threefold in diabetic as compared with control animals (0.31 +/- 0.04 vs. 0.11 +/- 0.01 nmol X mg protein-1 X 10 s-1). This accelerated influx corresponded to a three- to fourfold increase in the Vmax of alanine transport in diabetic versus control group (7.1 +/- 2.1 vs. 1.6 +/- 0.2 nmol X mg protein-1 X 10 s-1, P less than 0.05), whereas the Km of alanine uptake was unchanged (2.8 +/- 1.2 vs. 1.4 +/- 0.1 mM). Other neutral amino acids (20 mM) inhibited alanine transport to a similar degree in both groups. The sodium-dependent influx of glutamine (100 microM) was similar in diabetic and control groups (0.17 +/- 0.03 and 0.14 +/- 0.02 nmol X mg protein-1 X 10 s-1, respectively). The initial velocity of 22Na uptake (80 mM) into vesicles and half-maximal stimulation of alanine transport was achieved at essentially identical sodium concentrations (approximately 40 mM) in both groups.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Characterization of a sodium-dependent transport system for butyrobetaine into rat liver plasma membrane vesicles

Hepatology ◽  
1998 ◽  
Vol 28 (2) ◽  
pp. 521-525 ◽  
Author(s):  
Simona Berardi ◽  
Bruno Stieger ◽  
Sandra Wächter ◽  
Brigitte O'Neill ◽  
Stephan Krähenbühl
Keyword(s):  
Plasma Membrane ◽  
Rat Liver ◽  
Transport System ◽  
Membrane Vesicles ◽  
Plasma Membrane Vesicles ◽  
Liver Plasma Membrane ◽  
Sodium Dependent ◽  
Dependent Transport

scholarly journals Sensitivity of system A and ASC transport activities to thiol-group-modifying reagents in rat liver plasma-membrane vesicles. Evidence for a direct binding of N-ethylmaleimide and iodoacetamide on A and ASC carriers

1990 ◽  
Vol 271 (2) ◽  
pp. 297-303 ◽  
Author(s):  
E Pola ◽  
J Bertran ◽  
A Roca ◽  
M Palacín ◽  
A Zorzano ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Amino Acid ◽  
Rat Liver ◽  
Membrane Vesicles ◽  
Thiol Group ◽  
Transport Activity ◽  
Plasma Membrane Vesicles ◽  
Liver Plasma Membrane ◽  
System A ◽  
Alanine Transport

1. In the present study we have examined the sensitivity of A and ASC amino-acid-carrier activities in rat liver plasma-membrane vesicles to the thiol-group modifying reagents N-ethylmaleimide (NEM) and iodoacetamide (IA). To this end, the different Na(+)-dependent entities involved in alanine transport were assessed. 2. NEM inactivated Na(+)-dependent alanine transport as a result of the inhibition of both system A and ASC transport activities. The functional sensitivity of system A to NEM was greater than that of system ASC. 3. The presence of L-alanine (10 mM) during the exposure of vesicles to NEM afforded partial protection to system A, but not to the ASC, carrier. This effect was specific, since the presence of L-phenylalanine (10 mM) did not cause any protection. 4. Na+ did not protect A or ASC carriers against NEM inactivation; however, the presence of Na+ (100 mM-NaCl) and L-alanine (10 mM) during the exposure of the vesicles to NEM protected against inactivation of system A and ASC transport activities. The extent of protection was greater in the case of the system ASC transport activity than in the case of the A carrier. 5. IA also diminished Na(+)-dependent alanine transport by inhibition of A and ASC transport activities. Sodium and L-alanine afforded protection to both A and ASC transport activities from the inhibitory action of IA. The extent of protection induced by substrates was similar for both carriers. 6. It is concluded that there is one, or several, free thiol groups in A and ASC carriers, the integrity of which is essential for transport activity. Sensitivity to thiol-group-specific reagents and the pattern of protection with substrates against inactivation is different in A and ASC carriers. That suggests the existence of topological dissimilarities regarding the thiol-group containing site(s) in A and ASC amino acid carriers.

scholarly journals Comparison of the effects of certain thiol reagents on alanine transport in plasma membrane vesicles from rat liver and their use in identifying the alanine carrier

1983 ◽  
Vol 214 (2) ◽  
pp. 489-495 ◽  
Author(s):  
M R Hayes ◽  
J D McGivan
Keyword(s):  
Plasma Membrane ◽  
Concentration Dependence ◽  
Rat Liver ◽  
Transport System ◽  
Membrane Vesicles ◽  
Plasma Membrane Vesicles ◽  
Essential Component ◽  
Alanine Transport ◽  
Na Uptake

The Na+-dependent uptake of alanine into plasma membrane vesicles from rat liver was inhibited by N-ethylmaleimide (NEM) and by mersalyl. NEM did not inhibit alanine-independent Na+ uptake and the inhibition of alanine transport by NEM was protected by pre-incubation with an excess of substrate. It was therefore concluded that NEM acted by binding to the alanine carrier. A protein of Mr 20 000 was found to bind NEM with a concentration dependence parallel to the NEM inhibition of alanine transport. The inhibition of binding of [3H]NEM to this protein by mersalyl had a concentration dependence similar to that of the inhibition of transport by mersalyl. Preincubation with L-alanine, but not with D-alanine, led to protection of the Mr 20 000 protein from binding NEM. It is concluded that this protein is an essential component of the alanine transport system.

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