The Response of L5178Y-R and L5178Y-S Cells to X Rays under Oxic and Hypoxic Conditions

Abstract

SZUMIEL, I., BUDZICKA, E., NIEPOKOJCZYCKA, E., WtODEK, D., AND BEER, J. Z., The Response of L5178Y-R and L5178Y-S Cells under Oxic and Hypoxic Conditions. Radiat. Res. 87, 592-601 (1981). The response of two strains of murine lymphoma cells, L5178Y-R and L5178Y-S, to X rays applied under oxic or hypoxic conditions (produced by metabolic elimination of oxygen in dense cultures) was examined. It was found that Do values increased from 0.85 and 0.61 Gy under oxic conditions to 2.31 and 1.64 Gy under hypoxic conditions for L5178Y-R and L5178Y-S cells, respectively. Thus the oxygen enhancement ratio was ca. 2.7 for both strains. Inhibition of [3H]thymidine uptake, observed after exposure to X rays under oxic conditions, was more pronounced in L5178Y-S than in L5178Y-R cells. At the same time, L5178Y-S (but not L5178Y-R) cells showed an apparent increase in DNA content (as measured cytophotometrically). The rates of DNA synthesis and DNA content distribution were close to normal in both strains after irradiation under hypoxia. The results are compatible with the assumption that the slow rejoining of single-strand breaks in L5178Y-S cells [I. Korner, M. Walicka, W. Malz, and J. Z. Beer, Stud. Biophys. 61, 141-149 (1977)] is the cause of DNA synthesis inhibition and of the loosening of chromatin structure.