Intracellular Amino Acid Concentrations Research Articles

Change in intracellular concentration of free amino acids as a factor of euryhalinity in the crayfish Astacus astacus

1. 1. Astacus astacus survives in twice-diluted seawater in spite of the fact that the osmoregulatory mechanism which is active in freshwater maintains the concentration of the blood at an even higher level than that of the diluted seawater. 2. 2. In these conditions, the degree of hydration and the potassium content of the abdominal muscle show only a very slight modification. 3. 3. The adaptation results from an increase of intracellular concentration which is partly due to an increase of free amino acids. 4. 4. While the increase of blood concentration, in a crayfish transferred from fresh water to twice-diluted seawater, amounts to a change in Δ of 0·24°C, the increase in concentration of intracellular amino acids corresponds to 0·15°C, which shows that the free amino acids play an important role in the mechanism of adjustment.

The Intracellular Amino Acid Concentrations Required for Protein Synthesis in Cultured Human Cells

The Intracellular Amino Acid Concentrations Required for Protein Synthesis in Cultured Human Cells

AMINO ACID ACCUMULATION IN EHRLICH ASCITES CARCINOMA CELLS

Measurements of the transport of amino acids into Ehrlich ascites carcinoma cells have shown that the following relationship exists between the intracellular steady-state concentration of the amino acid (Cx) and the extracellular concentration (C0):[Formula: see text]where Cmis the maximum intracellular concentration (formed when C0is large) and Emis a constant. It is shown that Emis identical with Km, the Michaelis constant, if a carrier enzyme is involved in the process of active transport and is, therefore, a measure of the affinity of the amino acid for the effective agent involved in the transport phenomenon.The ratio of the steady-state intracellular and extracellular concentrations of amino acids exceeds unity with all amino acids examined. The responses of L-S-ethylcysteine transport to changes of potassium ion concentration and to changes of temperature differ from those of glycine transport and indicate that different carriers are involved in the active transport of these amino acids into Ehrlich ascites cells. This conclusion is supported by the fact that, whereas glycine and L-serine compete with each other for concentrative uptake, such mutual competition does not occur between S-ethylcysteine and glycine or L-serine or L-leucine.Effects of the metabolic inhibitors, 2,4-dinitrophenol, iodoacetate, and stilbestrol show that these substances exercise inhibitory effects on active transport of amino acids by suppression of respiratory or glycolytic energy. Stilbestrol, which is a particularly potent inhibitor, is more effective under aerobic conditions (in the absence of glucose) than under anaerobic conditions (in the presence of glucose). It is reasonable to account for these results on the hypothesis that the carrier responsible for amino acid transport is ATP dependent and that the carrier breaks down, and is no longer available for amino acid transfer, if the ATP content of the cell is depleted.

AMINO ACID ACCUMULATION IN EHRLICH ASCITES CARCINOMA CELLS

Measurements of the transport of amino acids into Ehrlich ascites carcinoma cells have shown that the following relationship exists between the intracellular steady-state concentration of the amino acid (Cx) and the extracellular concentration (C0):[Formula: see text]where Cmis the maximum intracellular concentration (formed when C0is large) and Emis a constant. It is shown that Emis identical with Km, the Michaelis constant, if a carrier enzyme is involved in the process of active transport and is, therefore, a measure of the affinity of the amino acid for the effective agent involved in the transport phenomenon.The ratio of the steady-state intracellular and extracellular concentrations of amino acids exceeds unity with all amino acids examined. The responses of L-S-ethylcysteine transport to changes of potassium ion concentration and to changes of temperature differ from those of glycine transport and indicate that different carriers are involved in the active transport of these amino acids into Ehrlich ascites cells. This conclusion is supported by the fact that, whereas glycine and L-serine compete with each other for concentrative uptake, such mutual competition does not occur between S-ethylcysteine and glycine or L-serine or L-leucine.Effects of the metabolic inhibitors, 2,4-dinitrophenol, iodoacetate, and stilbestrol show that these substances exercise inhibitory effects on active transport of amino acids by suppression of respiratory or glycolytic energy. Stilbestrol, which is a particularly potent inhibitor, is more effective under aerobic conditions (in the absence of glucose) than under anaerobic conditions (in the presence of glucose). It is reasonable to account for these results on the hypothesis that the carrier responsible for amino acid transport is ATP dependent and that the carrier breaks down, and is no longer available for amino acid transfer, if the ATP content of the cell is depleted.