Further studies on amino acid transport in murine P388 leukemia cells in vitro. Presence of system y⁺

The transport of glycine and l-lysine into murine P388 leukemia cells has been examined. Glycine transport appears to be shared by both systems A and ASC in P388 cells. Glycine transport is Na⁺-dependent and is effectively blocked by α-(methylamino)isobutyric acid, threonine and alanine but only a marginal reduction in transport is seen with 100-fold excess cold 2-aminobicyclo[2,2,1]heptane-2-carboxylic acid. System gly is not expressed in P388 cells. Lysine is largely transported by a Na⁺-independent, pH-insensitive system with a K_m of 0.079 mM. Lysine transport is relatively unafected by the addition of 100-fold excess cold α-(methylamino)isobutyric acid, 2-aminobicyclo[2,2,1]heptane-2-carboxylic acid and the anionic amino acids, l-glutamate and l-aspartate. A partial inhibition of lysine transport was observed with l-threonine and l-leucine while l-arginine and l-histidine radically decreased lysine transport. Lysine appears to be transported by a system similar to the system y⁺ seen in cultured human fibroblasts, Ehrlich ascites cells, and hepatoma cell lines.