The Effect of Gamma Radiation and Actinomycin on Cortisone Induction of Liver Enzymes

SummaryIonizing radiation and actinomycin-D were employed in an attempt to gain further insight into the mechanisms by which cortisone induces hepatic tyrosine transaminase (L-tyrosine: 2-oxoglutarate aminotransferase, EC 2.6.1.5) and tryptophan pyrrolase (L-tryptophan: H2O2 oxidoreductase, EC 1.11.1.4). Administration of the antibiotic at a dose of 200 μg/kg resulted in slight inhibition of the induction of tyrosine transaminase and tryptophan pyrrolase. Concomitant gamma radiation (6000 R) markedly enhanced this inhibition, while irradiation of the animals wthout actinomycin administration had little or no effect on the basal or induced levels of the enzymes studied. N2-di-methylene-actinomycin-C3, an analogue of actinomycin-D which does not bind to DNA, had no effect on enzyme induction.The authors thank Mrs. Annabelle Cutler for her excellent technical assistance.