Response of Lymphosarcoma LS/BL Cells to Continuous Irradiation

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Abstract
Mouse lymphosarcoma LS/BL cells growing as an ascite tumor in the peritoneal cavity of C57BL mice were continuously irradiated in vivo at a low exposure rate of 1.2 Gy [gray] per day (5 rad/h). The growth of the ascites tumor evaluated by direct counting of the cells in the peritoneal cavity and their capacity to form colonies in livers declined with increasing time of continuous irradiation. The radiosensitivity and repair ability of LS/BL cells were studied by a serial dilution method using host survival time as the end point and by the liver colony assay. The radiosensitivity of continuously irradiated LS/BL-CI cells showed no remarkable change as measured by the D0 [mean lethal dose] values, but from the 150th wk of irradiation the initial shoulder on the survival curves appeared and its width increased with time of exposure. The extrapolation number (n) increased from 1.0 to 8.4 after 350 wk of irradiation. The reappearance of the initial shoulder was proven with the split-dose technique.