Abstract
We have investigated certain events occurring in rat liver cytoplasm during the time period between the administration of hydrocortisone and the hormone-induced increase in the level of several hepatic enzymes. At various times after the administration of hydrocortisone to adrenalectomized rats, 14C-orotic acid was injected intraperitoneally. After a 40-min labeling period the rats were killed and liver cytoplasm was examined on sucrose gradients. Two hours post hydrocortisone administration the isotopic labeling of a 45 S cytoplasmic particle was markedly increased. Previous data suggest that the 45 S particle carries newly synthesized messenger RNA from the nucleus to the cytoplasmic polyribosomes. The stimulation of labeling occurred at a time consistent with the postulate that the excess of labeled RNA in the 45 S particle includes messenger RNA coding for the synthesis of the hormone-stimulated enzymes. A simultaneous fall in membrane-free, monomeric ribosomes was noted.
ACKNOWLEDGMENTS This work was supported by the U.S. Public Health Service Grant CA 03151 and by the American Cancer Society and the Leukemia Society, Inc. R.M.F. is a trainee of USPHS, Training Grant 1T4-CA 5167. E.C.H. is a Fellow of the Leukemia Society, Inc.
- Copyright ©, 1966, by Academic Press Inc.
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