The Catabolism of Tissue Nucleic Acid

Summary

The catabolism of RNA after total-body x-irradiation of rats was studied by labelling RNA with glucose-U-¹⁴C. The specific activities of urinary ribosyl imidazole acetate, as well as of RNA of liver, intestine, muscle, and spleen, were determined after x- or sham-irradiation. After exposure to 1000 r, the specific activity of urinary ribosyl imidazole acetate was increased, whereas that of intestinal and muscle RNA was decreased. The specific activity of RNA in lymphoid organs was also decreased after exposure to 756 r.

It is concluded that a radiation-induced increase in RNA catabolism is present mainly on the second and third day after exposure, primarily in intestine and muscle. In contrast, the starvation-induced increase in the catabolism of RNA occurs primarily in the liver and on the first day of starvation.