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Whole-body exposure of rats to 1000 R X-rays resulted in decreased rates in protein and RNA syntheses in the spleen from the fourth post-irradiation hour. These changes correspond well with impaired ability of nuclei to polymerise RNA, reduction in template efficiency of chromatin, decrease in the activity of RNA polymerase and inhibition in histone phosphorylation. Protection of the spleen by lead shielding during whole-body exposure to X-rays largely eliminated the observed alterations in protein and nucleic acid synthetic machineries. This suggests that the radiation-induced inhibition in protein and RNA syntheses is mainly due to the direct action of radiation on the spleen itself.

Exposure of rats to a single whole-body dose of X-rays led to an enhanced rate of RNA synthesis in the liver during 4 to 18 hours post-irradiation. This increase in RNA synthesis could not be obliterated by protecting the liver during irradiation. On the other hand, if adrenals were surgically removed prior to whole-body radiation exposure, no elevation either in liver RNA synthesis in vivo or liver chromatin template activity in vitro was apparent. Protection of only the head during irradiation could also prevent the stimulation in liver RNA synthesis in vivo. These results are suggestive of the involvement of neuro-endocrine reactions along the hypothalamus-pituitary-adrenal axes to be the underlying factors in whole-body radiation-evoked activation of the transcription machinery in the liver.