Biochemical radiosensitivity of lymphoid tumors.

The effect of whole-body irradiation on rat thymus, 3 differ ent mouse lymphosarcomas, and a mouse myeloid leukemia were studied. In thymus, myeloid leukemia, and C57BL-lymphosarcoma, the inhibition of nuclear adenosine-5'-triphosphate (ATP) synthesis and mitochondrial oxidative phosphorylation is demonstrated within a few hr after irradiation. The inhibition of nuclear ATP synthesis precedes the decrease of weight of the tissues, and of the DNA and ATP content of the nuclei after irradiation. In the Fr and CBA-lymphosarcoma, inhibition of nuclear ATP synthesis is much more delayed and no inhibi tion of mitochondrial oxidative phosphorylation is observed at the time when nuclear ATP synthesis is inhibited 50%. The cells which show the early inhibition of nuclear and mitochondrial ATP synthesis die exclusively or predominantly in interphase while the more radioresistant lymphoma cells (Fi and CBA) die in reappearing mitosis. A biochemical mechanism for radiation-induced cell death is proposed.