Effects of a Single Injection of Cortisol on Amino Acid-incorporating Activities of Rat Liver and Thymic Preparations in Vitro

Abstract

Abstract Cell-free homogenates prepared from thymic tissue of rats injected 3 hours prior to sacrifice with cortisol, as compared with similar preparations from control rat thymus, show an impaired capacity to incorporate amino acids into microsomal or ribosomal protein, and a diminished ribonucleic acid polymerase activity. In contrast, cell-free preparations from liver tissue of the same steroid-treated rats reveal an increase in amino acid incorporation by microsomes or ribosomes. The levels of activities of the pH 5.0 activating enzymes, cathepsin, and acid RNase are not altered significantly in thymic tissue of rats as a consequence of the cortisol treatment. In both thymus and liver, the locus of action of the steroid on amino acid incorporation is reflected at the same subcellular level, the ribosomes. Although the injection of cortisol resulted in a decrease in RNA polymerase activity of thymic homogenates, no positive evidence was obtained in preliminary studies that there was a deficiency of messenger RNA on ribosomes prepared from cortisol-treated rats.