The effects of cortisol on protein metabolism and on transfer ribonucleic acid methylase activity in rhabdomyosarcoma of rats.

The effects of cortisol on protein metabolism were examined in rhabdomyosarcoma tissue, experimentally provoked in rats by a single intramuscular injection of cobalt powder into the adductor muscle of the hind limb. In vivo treatment of tumour bearing animals with 1 and 10 mg cortisol resulted in a reduced incorporation of [2-14C] glycine into the tumour proteins. In vitro application of 0.01 to 100 micrograms cortisol on tumour slices equally reduced the amino acid incorporation into the proteins. These inhibitions could not be explained by modifications in protein, RNA, DNA content or by changes in the membrane function. The factors inhibiting the amino acid incorporation into tumour proteins could be located in the 105,000 X g supernatant protein fraction. The tumour transfer RNA methylase activity became markedly inhibited by cortisol treatment.