Early Events in the Effect of Hydrocortisone Acetate on Dna Replication in the Rat Brain

Abstract —Between the injection of hydrocortisone acetate to young rats and the onset of inhibition of DNA synthesis in brain, there is a lag period of 90 min. During these 90 min the only major alteration observed is a reduced formation of the DNA associated proteins while the synthesis of other brain proteins as well as that of RNA is normal. The specific activity of the enzymes thymidine kinase and DNA polymerase is also within control values. At later times, there is an inhibition in the synthesis of all brain proteins measured and of RNA and in the specific activity of the thymidine kinase. The specific activity of DNA polymerase remains normal throughout the period studied. These results indicate an important role for the DNA associated proteins in the regulation of DNA replication in rat brain.