The Catabolism of Nucleic Acids

Rats were injected with 3H-thymidine and three days later exposed to 500 r and 1000 r whole-body x-irradiation. The animals were sacrificed at various times after exposure and autoradiographs were prepared from spleen, thymus, testis, intestine, adrenals, liver, kidney and muscle. Autoradiographs were also prepared from a group of non-irradiated rats at different intervals after injection of 3H-thymidine. Extensive cell-destruction with subsequent phagocytosis of labelled nuclear debris by macrophages was observed in spleen and thymus. Cell and DNA-replacement was inhibited in the intestine, and the maturation of spermatogonia to primary spermatocytes seemed to be delayed in the testes of x-irradiated rats. Other organs of x-irradiated rats showed no significant alterations in their labelling pattern.