Mode of Action of Adrenal Cortical Hormones

II. Inhibition of Protein Synthesis in the Microsome-pH 5 Fraction System of Thymus Cells Following the Administration of Triamcinolone

Abstract

1. A study was carried out to clarify the nature of the impaired capacity of the thymus microsome-pH 5 fraction system to incorporate amino acids into proteins 2 to 3 hr after the administration of triamcinolone to rats.
2. The synthesis of amino-acyl-RNA in the pH 5 fraction [amino-acyl-RNA synthe-tases, EC 6. 1. 1 group] of 105, 000×g supernatant of thymus cells obtained from the rats treated with triamcinolone was significantly less than that from the control rats.
3. The incorporation of phenylalanine, lysine, and proline into microsomal proteins of rat thymus was stimulated by polyuridylic, polyadenylic, and polycytidylic acids, respectively. However, the stimulation of polyuridylic acid to incorporate phenylalanine into proteins of the thymus microsomes obtained from the hormone-treated rats was significantly less than that of thymus microsomes from the control rats.
4. It was suggested from these observations that both the soluble fraction and the ribosomes of thymus cells are involved in the inhibition of protein synthesis in thymus microsomes following the administration of adrenal cortical hormones.