A comparison of the ability of normal liver, a premalignant liver, a solid hepatoma and the Zajdela ascitic hepatoma, to take up amino acids in vitro.

The net total uptake of several amino acids at low (0.8-3.1 mumoles/liter) as well as high (800-1200 mumoles/liter) extracellular concentrations, by normal rat liver, a premalignant liver, a solid hepatoma, and the Zajdela ascitic hepatoma cells, has been compared under conditions in which protein synthesis continues. At low amino acid concentrations, the initial (3 min) total uptake of the various amino acids in the Zajdela cells, was 3-10 (average 7) times more, and the intracellular concentration of the labeled amino acids taken up 14-45 (average 31) times more, than in normal liver. At the high amino acid concentrations, the total uptake in the Zajdela cells, at 60-120 min was 2-5 (average 3.5) times more, and the intracellular concentration of the amino acids taken up 8-18 (average 13) times more, than in normal liver; the corresponding values for the premalignant liver and the solid hepatoma were in between those for normal liver and the Zajdela cells. Further, the rate of the total uptake of amino acids, their intracellular concentration, the proportion of the amino acid taken up utilized for protein synthesis, the rate of incorporation of the amino acid taken up into protein, and the cellular growth rate, seemed to be correlated in the four cell/tissue preparations studied. In most cases, the rate of the net uptake fell drastically with time, the uptake virtually stopping after 90-180 min, probably due to lack of serum in the incubation medium.