Time modulation effect of diethyldithiocarbamate (DDC) on radiosensitization by superoxide dismutase (SOD) inhibition.

Superoxide dismutase (SOD) is known to protect cells from the lethal effects of ionizing radiation by the dismutation of oxygen radicals. Diethyldithiocarbamate (DDC) is known inhibitor of SOD and may therefore be useful as a radiosensitizer. DDC however, is also a thiol radioprotector due to its ability to scavenge radiation induced free radicals. We have shown that DDC, if administered to tumours 1 hour prior to x-irradiation exerts a protective effect, whereas if administered 4 hours prior to irradiation, it radiosensitizes. This time modulation effect is not apparent after neutron irradiation where DDC protects in both situations. We have also examined the effect of DDC on the LD50/30 in mice after total body irradiation.