Effect of Continuous Irradiation on Proliferation of CHO - K 1 and xrs - 6 cells under Low and High Oxygen Conditions

The goals of this research were to determine: 1) the effect of continuous irradiation on Chinese Hamster Ovary cells, CHO-K1 (wild type) and xrs-6 cells (mutant), and 2) the effect of continuous irradiation under low (5%) and high (20%) ambient oxygen conditions. Other authors have found continuous irradiation at low dose rates to have beneficial effects on cells. Oxygen is known to be harmful to DNA as it induces free radicals. The CHO-K1 cells were continuously irradiated for 7 weeks on Am 241 foils at a photon dose rate of 1.76 ± 0.02 G The xrs-6 cells were irradiated for one week on the same foils. Using the CyQUANT assay, the CHO-K1 cells showed no statistically significant difference in proliferation between the irradiated and control cells, even for total accumulated doses (> 20 Gy) that are lethal when delivered acutely. The same result was observed with the xrs-6 cells. However, when plated in flasks as opposed to well-plates, the cells showed lower rates of proliferation when irradiated, by a factor of 2 for CHO-K1 and by a factor of 50 to 100 for xrs-6. There was no significant difference in proliferation of both cells lines in the low and high oxygen conditions. Thesis Supervisor: Jacquelyn C. Yanch Title: Professor