scholarly journals Characteristics of the transport of alanine, serine and glutamine across the plasma membrane of isolated rat liver cells

1978 ◽  
Vol 176 (3) ◽  
pp. 827-836 ◽  
Author(s):  
S K Joseph ◽  
N M Bradford ◽  
J D McGivan
Keyword(s):  
Amino Acids ◽  
Plasma Membrane ◽  
Isolated Hepatocytes ◽  
Liver Cells ◽  
Transport Systems ◽  
Cell Protein ◽  
Alanine Transport ◽  
Cell Plasma ◽  
Intracellular Content ◽  
Rat Liver Cells

1. Alanine, glutamine and serine were actively accumulated in liver cells isolated from starved rats. 2. This accumulation was inhibited when either Na+ or HCO3- ions were omitted from the incubation medium. In general the degree of dependence on Na+ was quantitatively similar to that on HCO3-. 3. The apparent Km values for the transport of all three amino acids were in the range 3–5mM with Vmax. values in the range 15–25nmol/min per mg of cell protein at 37 degrees C. 4. Alanine and serine transport were mutually competitive; glutamine inhibited the transport of alanine and serine non-competitively. 5. The initial rate of transport of these amino acids was inhibited when the intracellular content of ATP was decreased. 6. Ouabain inhibited the rate of alanine transport without inhibiting the rate of alanine metabolism. 7. It is concluded that a minimum of three transport systems must be postulated to exist in the liver cell plasma membrane to account for the transport of alanine, serine and glutamine. The rate of transport of these amino acids in isolated hepatocytes is unlikely to limit the rate at which they are metabolized.

scholarly journals Mechanism of the stimulation of serine and alanine transport into isolated rat liver cells by bicarbonate ions

1979 ◽  
Vol 182 (3) ◽  
pp. 697-705 ◽  
Author(s):  
J D McGivan
Keyword(s):  
Plasma Membrane ◽  
Isolated Hepatocytes ◽  
Preliminary Evidence ◽  
Weak Acid ◽  
Bicarbonate Ions ◽  
Alanine Transport ◽  
Rat Liver Cells ◽  
A Cell ◽  
Na Ions ◽  
Initial Difference

1. Bicarbonate ions stimulate the transport of serine and alanine into isolated hepatocytes. 2. The effect of bicarbonate is to increase the Vmax. of the transport process without changing the apparent Km. 3. The intracellular pH was estimated from the distribution of the weak base methylamine and the weak acid 5,5′-dimethyloxazolidine-2,4-dione (DMO) across the plasma membrane. 4. The addition of bicarbonate to a cell suspension caused the internal pH to become more acid. 5. The initial rate of serine, alanine and glycine transport was a linear function of the initial difference in pH across the membrane. 6. It is concluded that bicarbonate activates the transport of these amino acids primarily by increasing the pH difference across the plasma membrane. 7. It is suggested that the uptake of serine together with Na+ ions occurs in exchange for H+ ions, which are translocated outwards on the same carrier system. Some preliminary evidence consistent with this model is presented.

scholarly journals Transport of the aromatic amino acids into isolated rat liver cells. Properties of uptake by two distinct systems

1986 ◽  
Vol 233 (2) ◽  
pp. 499-506 ◽  
Author(s):  
M Salter ◽  
R G Knowles ◽  
C I Pogson
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Rat Liver ◽  
Transport System ◽  
Aromatic Amino Acids ◽  
Liver Cells ◽  
Transport Systems ◽  
Isolated Rat Liver ◽  
Rat Liver Cells ◽  
Isolated Rat

The transport of the aromatic amino acids into isolated rat liver cells was studied. There was a rapid and substantial binding of the aromatic amino acids, L-alanine and L-leucine to the plasma membrane. This has important consequences for the determination of rates of transport and intracellular concentrations of the amino acids. Inhibition studies with a variety of substrates of various transport systems gave results consistent with aromatic amino acid transport being catalysed by two systems: a 2-aminobicyclo(2,2,1)heptane-2-carboxylic acid (BCH)-insensitive aromatic D- and L-amino acid-specific system, and the L-type system (BCH-sensitive). The BCH-insensitive component of transport was Na+-independent and facilitated non-concentrative transport of the aromatic amino acids; it was unaffected by culture of liver cells for 24 h, by 48 h starvation, dexamethasone phosphate or glucagon. Kinetic properties of the BCH-inhibitable component were similar to those previously reported for the L2-system in liver cells. The BCH-insensitive component was a comparatively low-Km low-Vmax. transport system that we suggest is similar to the T-transport system previously seen only in human red blood cells. The results are discussed with reference to the importance of the T- and L-systems in the control of aromatic L-amino acid degradation in the liver.

scholarly journals Metabolic Studies of Amino Acids by Rat Liver Cells in Primary Culture

1978 ◽  
Vol 31 (6) ◽  
pp. 571-577
Author(s):  
Kyoichi KISHI ◽  
Yoshiaki FUJITA ◽  
Keiji TANAKA ◽  
Akira ICHIHARA
Keyword(s):  
Amino Acids ◽  
Primary Culture ◽  
Rat Liver ◽  
Liver Cells ◽  
Metabolic Studies ◽  
Rat Liver Cells

Transport of L-tyrosine by B16/F10 melanoma cells: the effect of the intracellular content of other amino acids

1990 ◽  
Vol 97 (3) ◽  
pp. 479-485
Author(s):  
J.R. Jara ◽  
J.H. Martinez-Liarte ◽  
F. Solano ◽  
R. Penafiel
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Initial Rate ◽  
Aromatic Amino Acids ◽  
Melanoma Cells ◽  
Transport Systems ◽  
Specific Amino Acid ◽  
Intracellular Content ◽  
Tyrosine Hydroxylation ◽  
In Cells

The uptake of L-Tyr by B16/F10 malignant melanocytes in culture has been studied. These melanoma cells can either be depleted of amino acids by 1 h preincubation in Hanks' isotonic medium or preloaded with a specific amino acid by 1 h preincubation in the same solution containing 2 mM of the amino acid to be preloaded. By means of these pretreatments, it is shown that the rate of L-Tyr uptake is greatly dependent on the content of other amino acids inside the cells. The L-Tyr uptake is higher in cells preloaded with amino acids transported by the L and ASC systems than in cells depleted of amino acids or preloaded with amino acids transported by the A system. It is concluded that L-Tyr is mainly taken up by an exchange mechanism with other amino acids mediated by the L1 system, although the ASC system can also participate in the process. In agreement with that, the homo-exchange performed by cells preloaded with unlabelled L-Tyr is more efficient than any other hetero-exchange, although L-Dopa, the product of tyrosine hydroxylation in melanin synthesis, is almost as efficient as L-Tyr. Apart from aromatic amino acids, melanoma cells preloaded with L-Met and L-His also yield a high initial rate of L-Tyr uptake. The results herein suggest that melanoma cells do not have transport systems specific for L-Tyr, even if this amino acid is needed to carry out the differential pathway of this type of cells, melanosynthesis.

Impaired alanine uptake by basolateral liver plasma membrane vesicles from rats consuming ethanol

1991 ◽  
Vol 261 (6) ◽  
pp. G913-G920
Author(s):  
D. J. Smith ◽  
S. A. Ploch
Keyword(s):  
Plasma Membrane ◽  
Lipid Composition ◽  
Cholesterol Content ◽  
Ethanol Consumption ◽  
Chronic Ethanol ◽  
Transport Systems ◽  
Liver Plasma Membrane ◽  
Alanine Transport ◽  
Chronic Ethanol Consumption ◽  
Induced Changes

Chronic ethanol consumption reduces alanine transport by rat basolateral liver plasma membrane (blLPM) vesicles; however, the mechanism for this effect remains uncertain. It may be related to the ethanol-induced changes in blLPM fluidity and lipid composition; alternatively ethanol might reduce the number of transporters in the blLPM. To investigate the effect of blLPM fluidity and lipid composition on Na(+)-dependent alanine uptake these parameters were altered in vitro. Increasing the blLPM fluidity had no effect on Na(+)-dependent alanine uptake by blLPM vesicles or the activity of amino acid transport systems, A and ASC. Because ethanol is known to reduce the blLPM cholesterol content, the influence of altering blLPM cholesterol on alanine transport by these membranes was investigated next. Neither an increase nor a decrease of the cholesterol content of the blLPM altered Na(+)-dependent alanine uptake or the activity of system A or ASC. Finally, the influence of chronic ethanol consumption on the specific binding of [3H]alanine to blLPM was studied. The dissociation constant for alanine binding to blLPM from ethanol-fed rats and their pair-fed controls was similar (1.9 +/- 0.2 vs. 2.0 +/- 0.3 mM); however, the maximal binding capacity for alanine was significantly (P less than 0.05) lower in the blLPM from ethanol-fed rats (316 +/- 53 pmol/mg protein) compared with their pair-fed controls (527 +/- 79 pmol/mg protein). These studies do not support the hypothesis that ethanol-induced changes in blLPM fluidity are responsible for the impaired alanine transport; they do suggest that ethanol may reduce the

scholarly journals Polyribosomes in isolated liver cells. Preparative procedures, effects of incubation and correlation with protein synthesis

1980 ◽  
Vol 186 (1) ◽  
pp. 35-45 ◽  
Author(s):  
A J Dickson ◽  
C I Pogson
Keyword(s):  
Protein Synthesis ◽  
Rat Liver ◽  
Isolated Hepatocytes ◽  
Liver Cells ◽  
Liver Protein ◽  
Isolated Cells ◽  
Isolated Liver Cells ◽  
Rat Liver Cells ◽  
Isolated Liver

Methods have been derived which permit the isolation of undergraded polyribosomes from isolated rat liver cells. Under the conditions used the polyribosome profile of hepatocytes immediately after isolation was essentially identical with that from intact liver. However, during incubation of cells in complex physiological media there was a progressive dissociation of polyribosomes. The addition of a variety of factors that produce reaggregation of polyribosomes in rat liver in vivo did not prevent dissociation during cell incubations. Although large polyribosomes were lost most rapidly, the albumin-synthesizing capacity of isolated cells was not selectively lost when compared with total protein synthesis. The significance of these results for the use of isolated hepatocytes in the study of liver protein synthesis is discussed.

scholarly journals The effects L-leucine on the synthesis of urea, glutamate and glutamine by isolated rat liver cells

1975 ◽  
Vol 146 (2) ◽  
pp. 457-464 ◽  
Author(s):  
J M Mourão ◽  
J D McGivan ◽  
J B Chappell
Keyword(s):  
Amino Acids ◽  
Nitrogen Source ◽  
Glutamate Dehydrogenase ◽  
Rat Liver ◽  
Liver Cells ◽  
Carbamoyl Phosphate ◽  
Isolated Cells ◽  
Isolated Rat Liver ◽  
Rat Liver Cells ◽  
Isolated Rat

With either alanine or a mixture of 15 different amino acids as nitrogen source, the addition of L-leucine inhibited the synthesis of urea by isolated rat liver cells. With alanine present leucine promoted the production of glutamate and glutamine. Comparison of effects of leucine on soluble glutamate dehydrogenase, mitochondria and isolated cells supports the postulate that leucine exerts its effect through activation of glutamate dehydrogenase. It is suggested that this latter enzyme may not be as important for the production of NH3 for carbamoyl phosphate synthesis as has been considered hitherto.

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