Differences in the Effect of Ionizing Radiation on Na+-Dependent Amino Acid Transport in Human T (Molt-4) and Human B (RPMI 1788) Lymphoid Cells

We have investigated the effects of ionizing radiation (0.10 to 10 krad) on the Na+-dependent transport of 2-aminoisobutyric acid and the involvement of a plasma membrane sulfhydryl-protein component which modulates this transport system in a human T (Molt-4) and a B (RPMI 1788) lymphoid cell line. The radiosensitivity of this transport system and a putative sulfhydryl membrane regulatory component correlated with the known radiosensitivity of these two cell lines, i.e., DNA synthesis and survival, were much more sensitive to the effects of γ irradiation in Molt-4 than in RPMI 1788 cells. Ionizing radiation affected Na+-dependent amino acid transport in Molt-4 cells by a process which affects the maximal rate of uptake of the amino acid (i.e., V max) into the cell. No change in Na+-independent amino acid transport was observed when Molt-4 cells were subjected to radiation levels as high as 5 krad. These data coupled with the observations from other laboratories have led us to hypothesize that the radiatio...