scholarly journals Ion gradients and the accumulation of various amino acids by mouse ascites-tumour cells depleted of adenosine of adenosine triphosphate

1969 ◽  
Vol 112 (1) ◽  
pp. 11P-12P ◽  
Author(s):  
A A Eddy ◽  
C Hogg ◽  
M Reid
Keyword(s):  
Amino Acids ◽  
Adenosine Triphosphate ◽  
Tumour Cells ◽  
Ascites Tumour ◽  
Ion Gradients ◽  
Mouse Ascites ◽  
Ascites Tumour Cells

scholarly journals Ionophore-mediated coupling between ion fluxes and amino acid absorption in mouse ascites-tumour cells. Restoration of the physiological gradients of methionine by valinomycin in the absence of adenosine triphosphate

1974 ◽  
Vol 140 (3) ◽  
pp. 383-393 ◽  
Author(s):  
M. Reid ◽  
L. E. Gibb ◽  
A. A. Eddy
Keyword(s):  
Amino Acid ◽  
Sodium Pump ◽  
Tumour Cells ◽  
Ascites Tumour ◽  
Maximum Value ◽  
Methionine Concentration ◽  
Mouse Ascites ◽  
Na Ions ◽  
Physiological Gradients ◽  
Ascites Tumour Cells

1. Preparations of mouse ascites-tumour cells depleted of ATP and Na+ ions accumulated l-methionine, in the presence of cyanide and deoxyglucose, from a 1mm solution containing 80mequiv. of Na+/l and about 5mequiv. of K+/l. Valinomycin increased, from about 4 to 16, the maximum value of the ratio of the cellular to extracellular concentrations of methionine formed under these conditions without markedly affecting the distributions of Na+ and of K+. Similar observations were made with 2-aminoisobutyrate, glycine and l-leucine. Increasing the extracellular concentration of K+ progressively decreased the accumulation of methionine in the presence of valinomycin. Over the physiological range of ionic gradients, the system behaved as though the absorption of methionine with Na+ was closely coupled to the electrogenic efflux of K+ through the ionophore. The process was insensitive to ouabain and so the sodium pump was probably not involved. 2. The amount of methionine accumulated during energy metabolism was similar to the optimal accumulation in the presence of valinomycin when ATP was lacking. It was also similarly affected by increasing the methionine concentration. 3. A mixture of nigericin and tetrachlorosalicylanilide mimicked the action of valinomycin. The anilide derivative inhibited the absorption of 2-aminoisobutyrate in the presence of valinomycin, but not in its absence. 4. Gramicidin inhibited methionine absorption and caused the preparations to absorb Na+ and lose K+. 5. The observations appear to verify the principle underlying the gradient hypothesis by showing that the tumour cells can efficiently couple the electrochemical gradient of Na+ to the amino acid gradient.

scholarly journals Metabolism and sodium transfer of mouse ascites tumour cells

1958 ◽  
Vol 140 (1) ◽  
pp. 80-93 ◽  
Author(s):  
M. Maizels ◽  
Mary Remington ◽  
R. Truscoe
Keyword(s):  
Tumour Cells ◽  
Ascites Tumour ◽  
Sodium Transfer ◽  
Mouse Ascites ◽  
Ascites Tumour Cells

scholarly journals The accumulation of amino acids by mouse ascites-tumour cells. Dependence on but lack of equilibrium with the sodium-ion electrochemical gradient

1981 ◽  
Vol 194 (2) ◽  
pp. 415-426 ◽  
Author(s):  
C Hacking ◽  
A A Eddy
Keyword(s):  
Amino Acids ◽  
Steady State ◽  
Amino Acid ◽  
Rate Coefficient ◽  
Tumour Cells ◽  
Cellular Respiration ◽  
Mouse Ascites ◽  
Predicted Values ◽  
Leak Pathway ◽  
Ascites Tumour Cells

1. The fluorescent dye 3,3′-dipropyloxadicarbocyanine was used to show that the tumour cells absorbed 2-aminoisobutyrate, glycine, L-leucine and L-isoleucine and certain other amino acids electrogenically. The Km values with respect to amino acid concentration ([A]o), obtained from the fluorescence assays, varied through the above series from 0.8 to 26 mM, with Vmax. fairly constant. 2. Similar Km values described the uptake of the 14C-labelled amino acids in five instances where this was measured. 3. Each amino acid lowered the membrane potential (E) by 10-20 mV when its cellular concentration ([A]i) had reached a steady value and [A]o was 10mM. In these experiments energy metabolism was maintained by glycolysis, 2,4-dinitrophenol was present and cellular respiration was inhibited. The corresponding net flow of amino acid through the Na+ symport was deduced by making use of the fact that the depolarization an amino acid initially caused was roughly proportional to the net influx of amino acid itself. 4. The steady-state depolarization was attributed to the presence of a leak pathway for the amino acid with a rate coefficient PA. As assayed in the absence of Na+, PA was about 5-fold larger for isoleucine than for glycine. 5. Direct estimates of Vmax./PA were similar to those inferred from the extent of depolarization in the steady state and [A]i. 6. A mathematical model was used to predict [A]i/[A]o in term of the measured values of [Na]o, [Na]i, E, Km and Vmax./PA. The predicted and observed values agreed fairly well when [A]o was 1 mM or 10 mM. 7. [A]i/[A]o varied from about 2.5 for 10 mM-isoleucine to 30 for 1 mM-2-aminoisobutyrate when delta microNa, expressed as a ratio, was ostensibly in the range 19-43. 8. The concentration of 2-aminoisobutyrate from a 0.1 mM solution in the presence or absence of ouabain was consistent with the model, whereas the concentration of isoleucine from a 0.1 mM solution exceeded the predicted values 2-5-fold. 9. The tumour cells concentrated 2-amino-bicyclo[2,2,1]heptane-2-carboxylic acid by a non-electrogenic mechanism, with which isoleucine may also interact.

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