Radiation and actinomycin D mortality studies: circadian variations in lethality due to independent effects of either agent.

Abstract

SummaryC57BL/6 mice were exposed to either ionizing radiation or actinomycin at the peak and nadir of jejunal crypt cell mitotic activity. Animals exposed at the peak were more sensitive than animals exposed at the nadir. Conversely, animals treated with actinomycin D were slightly more sensitive at the nadir. These observations suggest that studies of the combined lethal effects of ionizing radiation and actinomycin D may be complicated by the change in sensitivity of normal tissues to either treatment under the influence of a circadian variable.