Effect of irradiation on the biosynthesis of liver ribonucleic acids in intact and adrenalectomized rats.

Intact and adrenalectomized rats were irradiated with 900 R or treated with 10 mg per 100 g body weight of hydrocortisone. The incorporation of orotic acid-6-14C for 2 hours into liver free uridine nucleotides, nuclear and cytoplasmic RNA and RNA fractions obtained by agar gel electrophoresis, were studied. The obtained results show that in intact animals both irradiation and hydrocortisone induce a higher labelling of cytoplasmic and nuclear liver RNA. The higher labelling of RNA is not correlated with a higher labelling of the free uridine nucleotides. The labelling of all electrophoretic RNA fractions is increased to approximately the same extent under the action of either hydrocortisone or irradiation. Irradiation or hydrocortisone treatment of adrenalectomized rats causes also a higher labelling of liver nuclear and cytoplasmic RNA. The higher labelling of RNA is not correlated with that of free uridine nucleotides and affects all electrophoretic RNA fractions.. The combined action of irradiation and hydrocortisone shows an additive effect on the labelling of nuclear and cytoplasmic liver RNA. The obtained results indicate that whole body irradiation causes an increased synthesis of both ribosomal and non-ribosomal RNA’s of rat liver. Since the same effect is observed in intact and adrenalectomized animals it may be concluded that the stimulation of liver RNA synthesis by irradiation is not mediated by the adrenals.