J. Biochem, 1968, Vol. 63, No. 2 176-185
© 1968 Japanese Biochemical Society
research-article |
Mode of Action of Adrenal Cortical Hormones
I. Effect of Corticosteroids on Amino Acid Incorporation into Proteins of Thymus and Liver Subcellular Components in Cell-free Systems
Kitano Hospital Tazuke Kofukai Medical Research Institute Kita-ku, Osaka
1. The effect of adrenal cortical hormones (corticosterone and triamcinolone) on amino acid incorporation into protiens of nuclei, mitochondria, and microsomes of rat thymus and liver was studied in cell-free systems.
2. Corticosterone, the principal natural glucocorticoid in rats, and triamcinolone, a synthetic glucocorticoid, at concentrations of 2x10–4 to 10–6 M, inhibited amino acid incorporation into nuclear and mitochondrial proteins of the thymus in vitro. However, these steroids, in vitro, did not affect amino acid incorporation into microsomal proteins of the thymus. The inhibiting effect on amino acid incorporation into nuclei of thymus cells was observed within 20 min of incubation at 37°C at a concentration greater than 2x10–6
3. The administration of adrenal cortical hormones to rats inhibited amino acid incorporation into proteins of all subcellular components of thymus cells, including nuclei, mitochondria, and microsomes.
4. Adrenal cortical hormones inhibited amino acid incorporation into thymus nuclear proteins both in vivo and in vitro. However, amino acid incorporation into microsomal proteins of thymus cells was inhibited by adrenal cortical hormones only in vivo, but not in vitro. This observation suggests an important role of nuclei in the action of adrenal cortical hormones in inhibiting protein synthesis in thymus cells.
5. Under the same conditions these steroids did not inhibit amino acid incorporation into proteins of all subcellular fractions of liver cells such as nuclei, mitochondria, and microsomes.