Radiation-induced Tissue Breakdown

1. An attempt was made to determine the source of excess 14C -labelled glycine and phenylalanine observed in ‘free’ metabolic pools of rats loaded with glycine-2-14C and phenylalanine-3-14C before irradiation. 2. Tissues from various organs of irradiated and non-irradiated rats were fractionated into three protein fractions. Glycine, phenylalanine, tyrosine, serine and alanine were isolated from these fractions, and the respective specific activities were determined. 3. Differences in specific activities were : decreased activity in muscle collagen and soluble-protein fractions of thymus and spleen; increased activity in soluble-protein fractions of liver and muscle; and variable changes in the activity of certain amino acids of the soluble-protein fraction of kidney. 4. The significance of these changes is discussed in terms of known biological effects of radiation on cells and cellular metabolism. 5. Muscle collagen seems radio-sensitive and its increased catabolism in irradiated rats could explain much of the excess 14C-activity in ‘free’ -amino-acid pools.