Adrenocorticotrophin and Adrenal Protein Synthesis1

Abstract

In vitro protein synthesis by a cell-free preparation (15,000 × g supernatant fraction) of pig adrenals was studied, measuring glycine-¹⁴C and Z-leucine-¹⁴C incorporation into protein. Adrenocorticotrophin administered to rats in vivo caused a significant increase in the total activity of nondialyzable “supernatant factor” stimulating amino acid incorporation into protein. The specificity of the observed effect for adrenocorticotrophin was confirmed by experiments with both a synthetic tricosapeptide and a highly purified preparation obtained from natural sources. The “supernatant factor” was nondialyzable, had an approximate molecular weight of 10-14 × 10⁴, and was inactivated by incubation at 55 C and also by incubation with trypsin. It was not inactivated by ribonuclease. Nucleic acids prepared by several methods were inactive. The “supernatant factor’ could be purified by diethylaminoethyl cellulose chromatography, and chemical analysis revealed the protein nature of the material with virtually no ribonucleic acid present in the preparation. It is tentatively concluded that this material is one of the transfer enzymes involved in protein synthesis, several other possibilities having been excluded. (Endocrinology76: 745, 1965)