RT Journal Article SR Electronic T1 The Effect of Cortisol, Administered in Vivo, on the in Vitro Incorporation of DNA and RNA Precursors by Rat Thymus Cells JF Molecular Pharmacology JO Mol Pharmacol FD American Society for Pharmacology and Experimental Therapeutics SP 219 OP 224 VO 3 IS 3 A1 WILLIAM B. PRATT A1 STEVEN EDELMAN A1 LEWIS ARONOW YR 1967 UL http://molpharm.aspetjournals.org/content/3/3/219.abstract AB Cortisol, administered in vivo, decreases the rate at which radioactive labeled deoxycytidine and uridine are incorporated into macromolecular material by rat thymus cells incubated in vitro. The degree of inhibition of uridine conversion to acid-insoluble material, observed after 3 hr of cortisol treatment, remains constant at both high and low levels of precursor specific activity, whereas the inhibition of deoxycytidine-3H incorporation observed using precursor of high specific activity is obliterated when the labeled precursor is diluted with large amounts of the nonradioactive compound. This observation is consonant with the hypothesis that one action of cortisol on rat thymocytes is to increase the intracellular pool of DNA precursors and not, as has been supposed, to inhibit the rate of DNA synthesis. Inhibition of RNA synthesis does seem to occur within a few hours after cortisol administration. ACKNOWLEDGMENTS This work was supported by Grant CAO5672 from the National Cancer Institute, National Institutes of Health, and Public Health Service Training Grant GM322 from the Division of General Medical Sciences.