Thermal sensitivity and radiosensitization in V79 cells after BrdUrd or IdUrd incorporation

Chinese hamster V79 cells were exposed to 10(-5) moles/liter bromodeoxyuridine (BrdUrd) or iododeoxyuridine (IdUrd) for 16 or 29 hr and then tested for thermal sensitivity, radiosensitivity, and sensitivity to the combined treatments of heat and radiation. BrdUrd and IdUrd treatment of cells resulted in enhanced radiosensitivity which increased with exposure time but had little or no effect on thermal sensitivity. For 42.0 degrees C heating, no effect was observed, while for 45.0 degrees C heating, a small decrease in thermal sensitivity occurred for both 16- and 29-hr exposure times, in the combined treatment of heat and radiation, the presence of BrdUrd or IdUrd resulted in about the same thermal enhancement in radiosensitivity. BrdUrd and IdUrd uptake into cellular DNA were measured using high-pressure liquid chromatography and, after a 29-hr exposure to 10(-5) moles/liter of BrdUrd or IdUrd, approximately 40% of the thymidine was substituted.