Repair of Sublethal Radiation Injury in Hypoxic Cells of a C 3 H Mouse Mammary Carcinoma

Abstract

The cells of a C3H mouse mammary carcinoma were examined for their ability to repair sublethal radiation injury using the split-dose technique and ${\rm TCD}_{50}$ as the end point ( ${\rm TCD}_{50}$ = radiation dose that yields local control of half of the irradiated tumors). Radiation was administered either under conditions of local tissue hypoxia (application of a clamp across the root of the thigh bearing the tumor for 2 minutes prior to and during irradiation) or under ${\rm O}_{2}30 {\rm psi}$ conditions (respiring pure oxygen at 3 atmospheres of pressure absolute for 15 minutes prior to and during irradiation). The ${\rm TCD}_{50}$ values were 5372 rads for v = 1 (single dose) and 6853 rads for v = 2 ( $D_{1}=3000$ rads, hypoxia; $t_{i}=6 \text{hours}$ ; $D_{2}=\text{variable}$ , hypoxia). Thus, these acutely hypoxic mammary carcinoma cells repaired rad...