Radiosensitivity of Ehrlich Ascites Tumor Cells in Different Growth Phases and its Enhancement by lodoacetamide

The x-ray survival curve of Ehrlich ascites tumor cells and its modification by iodoacetamide were determined by the TD50, assay. Survival curves for tumor cells of 1, 6 and 12-days after transplantation were examined in the presenc or in the absence of the agent. The D0 was 130, 350 or 230 rads for 1-, 6 and 12-day-old tumor cells, respectively. The response to x-rays of 1 and 6-day-old tumor cells was enhanced by iodoacetamide, while that of 12-day-old or stationary phase tumor cells was hardly enhanced. The increased radiosensitivity and the lowered sensitization by iodoacetamide of 12-day-old tumor cells might be attributed to an increased proportron of the stationary phase cells.