Effects of X-irradiation on the Synthesis of Rapidly Labelled RNA in an Experimental Tumour of the Rat

SummaryEffects of ionizing radiations on the synthesis of rapidly labelled RNA were studied on the Yoshida ascites hepatoma cells (AH 130) of the rat, at different intervals (0·5, 1·5, 4, 20 hours) after a whole-body x-irradiation of 1000 R.An increase was observed in the incorporation of 3H-5-uridine into rapidly labelled RNA, notably into the RNA of high molecular weight, when the irradiated cells were labelled in vivo.In contrast, when the irradiated cells were labelled in vitro, a slight inhibition or no change was observed in the synthesis of the rapidly labelled RNA.The reason for the difference between the results of in vivo and in vitro experiments was discussed.