scholarly journals Further observations on the inhibitory effect of extracellular potassium ions on glycine uptake by mouse ascites-tumour cells

1969 ◽  
Vol 114 (4) ◽  
pp. 807-814 ◽  
Author(s):  
A A Eddy ◽  
M. C. Hogg
Keyword(s):  
Initial Rate ◽  
Inhibitory Effect ◽  
Sodium Cyanide ◽  
Tumour Cells ◽  
Extracellular Potassium ◽  
Potassium Ions ◽  
Atp Content ◽  
Entry Rate ◽  
Mouse Ascites ◽  
Ascites Tumour Cells

1. The initial rate of uptake of glycine by the tumour cells was measured as a function of the Na+ and K+ concentrations in the solution in which the cells were suspended. When [Gly] was 1mm or 12mm, the rate in the absence of Na+ was independent of [K+] and about 3% or 10% respectively of the rate when [Na+] was 150m-equiv./l. 2. The Na+-dependent glycine entry rate, v, at a given value of [Na+] was successively lowered when [K+] was increased from 8 to 47 to 96m-equiv./l. A kinetic analysis indicated that K+ competitively inhibited the action of Na+. The results were in fair agreement with previous determinations of the kinetic parameters. 3. The presence of 2mm-sodium cyanide and 10mm-2-deoxyglucose lowered the cellular ATP content to less than 3% of the value in the respiring cells. Although v was then about 50% smaller, the relative effects of K+ and Na+ on the system were similar to those observed during respiration. 4. A theoretical analysis indicated that the variation of v with [K+] is not a reliable guide to the extent to which the K+ gradient between the cells and their environment may contribute to the net transport of glycine.

scholarly journals The effects of varying the cellular and extracellular concentrations of sodium and potassium ions on the uptake of glycine by mouse ascites-tumour cells in the presence and absence of sodium cyanide

1968 ◽  
Vol 108 (3) ◽  
pp. 489-498 ◽  
Author(s):  
A A Eddy
Keyword(s):  
Sodium Cyanide ◽  
Maximum Amount ◽  
Tumour Cells ◽  
Potassium Ions ◽  
Concentration Gradients ◽  
Spontaneous Movements ◽  
Mouse Ascites ◽  
Sodium And Potassium ◽  
Ascites Tumour Cells ◽  
Respective Concentration

1. Tumour cells were starved to deplete them of ATP and transferred to 0·9mm-glycine in Ringer solutions containing 2mm-sodium cyanide and various Na+ and K+ concentrations. The uptake of glycine then usually reached a peak by about 10min. 2. When cellular [Na+] and extracellular [Na+] were each about 30m-equiv./l., the maximum amount of glycine absorbed increased between 1·2- and 3·0-fold on lowering extracellular [K+] from 128 to 10m-equiv./l. 3. When extracellular [Na+] was 150m-equiv./l., the ratio, R, of the cellular to extracellular glycine concentrations increased progressively, from near 1 to about 9, when cellular [Na+] was lowered from 120 to 40m-equiv./l. 4. When cellular [Na+] was almost constant, either at 45 or 70m-equiv./l., R fell about 14-fold when extracellular [Na+] varied from 150 to 16m-equiv./l. 5. Values of R near 0·2 were found when cellular [Na+] was about four times as large as extracellular [Na+]. 6. R fell about threefold when the cells were put with 12mm- instead of 0·9mm-glycine. 7. The results were taken to imply that, under these conditions, the spontaneous movements of both Na+ and K+ across the cell membrane, down their respective concentration gradients, served to concentrate the glycine in the tumour cells (Christensen's hypothesis).

scholarly journals A net gain of sodium ions and a net loss of potassium ions accompanying the uptake of glycine by mouse ascites-tumour cells in the presence of sodium cyanide

1968 ◽  
Vol 108 (2) ◽  
pp. 195-206 ◽  
Author(s):  
A A Eddy
Keyword(s):  
Ringer Solution ◽  
Sodium Cyanide ◽  
Tumour Cells ◽  
Potassium Ions ◽  
Carrier System ◽  
Mean Values ◽  
Spontaneous Movements ◽  
Mouse Ascites ◽  
The Mean ◽  
Ascites Tumour Cells

1. The tumour cells were starved in a solution lacking Na+ and then transferred to a Ringer solution containing 2mm-sodium cyanide, 150m-equiv. of Na+/l. and 10m-equiv. of K+/l. Such cells were depleted of ATP and contained an endogenous pool of various amino acids equivalent to a 26mm solution. 2. At 4min. after the transfer the cellular Na+ content had increased by about 100% and roughly an equivalent amount of K+ had left the cells. 3. Under these conditions [14C]glycine was absorbed from an 11mm solution and reached the same cellular concentration by about 4min. The pool size increased by approximately the same amount (ΔGly), so glycine did not simply exchange with the endogenous components. 4. After 4min. with glycine, the cells contained about 20% more Na+ (ΔNa+) than the control and about 10% less K+ (ΔK+). The mean values of ΔNa+/ΔGly and ΔK+/ΔGly from five experiments were respectively 0·90±0·11 and 0·62±0·11equiv./mole. 5. A further indication that these two ratios were not equal was that the cells absorbed more water than the movement of glycine itself required. The excess of water was osmotically equivalent to 0·95±0·16equiv. of solute/mole of glycine absorbed. 6. The variation of ΔNa+/ΔGly with the duration of the incubation was consistent with the stimulated uptake of Na+ being linked to the actual transport of glycine. The same may apply to the movement of K+, though the time-dependence was not examined in that case. 7. The observations were analysed in terms of a model in which both K+ and Na+ moved with a glycine-carrier system without ATP being involved. The analysis supported the idea that the spontaneous movements of the ions through the system might concentrate glycine in the cells significantly by purely physical means (Christensen's hypothesis).

scholarly journals A sodium ion concentration gradient formed during the absorption of glycine by mouse ascites-tumour cells

1969 ◽  
Vol 115 (3) ◽  
pp. 505-509 ◽  
Author(s):  
A A Eddy
Keyword(s):  
Concentration Gradient ◽  
Ringer Solution ◽  
Sodium Cyanide ◽  
Tumour Cells ◽  
Sodium Ion ◽  
Ion Concentration ◽  
Carrier System ◽  
Parallel Movement ◽  
Mouse Ascites ◽  
Ascites Tumour Cells

1. To deplete them of ATP the tumour cells were starved at 37° in a Ringer solution containing 33m-equiv. of Na+/l., 131m-equiv. of Li+/l., 2mM-sodium cyanide and 0·1mm-ouabain. The cellular content of K+ was largely replaced by Li+, but cellular [Na+] remained near 33m-equiv./l. 2. The addition of 12mm-glycine to the system caused cellular [Na+] to increase, during the next 4min., by about 4m-equiv./l., so that it slightly exceeded extracellular [Na+]. This occurred in parallel with the absorption of glycine. 3. The cellular K+ content fell by an amount representing about 10% of the amount of Na+ absorbed. 4. The results provide a clear demonstration that the flow of glycine into the cells is linked to a parallel movement of Na+; K+ appears to play a facultative role in the carrier system, whereas Li+ is almost inert. 5. The effects produced by glycine were not reproduced by l-arabinose.

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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