Single-Dose and Split-Dose X-Ray Studies of the Radio-Sensitivity of Autochthonous Radiation-Induced Lymphosarcomas in C57BL Mice

Abstract

Observations extending back many years have indicated that the lymphocyte and its malignant counterpart are more radiosensitive than most other normal or malignant cell lines. As improved methods for testing cellular radiosensitivity have become available, it has been possible to evaluate the sensitivity of these cells in a more quantitative and meaningful manner. There are several reports of radiation dose-response studies in serially transplanted murine lymphoid tumors. Hewitt and Wilson found a D37 of 162 rads and an extrapolation number of 1.5 (1). Berry and Andrews reported a similar D37 of 160 rads with an extrapolation number of 1.6 (2); Powers and Tolmach have found a D37 of 110 R with an extrapolation number of 1.2 (3); and Bush and Bruce have reported D37's of 114 and 165 rads for the same lymphoid tumor when different assay methods were used (4, 5). Recent in vivo and in vitro indirect measurements of the radiosensitivity of various immunologic functions of normal lymphocytes have given D37's of 47 R to 78 R (6-8) with extrapolation numbers of 1.8 to 3.2. Measuring lymphocyte death in an in vitro system, Trowell has obtained a D37 of approximately 140 R with an extrapolation number of 1.0 (9). There are no split radiation dose studies of the recovery rate of normal or malignant lymphocytes. The desirability of doing such studies in autochthonous systems was not generally recognized until Scott and others called attention to the potential pitfalls of subtle immunologic influences and cytogenetic alterations which may accompany serial transplantation (10-15). The induction of thymic lymphosarcomas in strain C57BL