Alterations in vitro of amino acid incorporating activity of liver preparations of non-starved normal and stress-induced rats

Abstract

Acute stress was induced 4.5 h before decapitation in non-starved rats by a single intraperitoneally injection of 10 mg Celite per 100 g body weight. Incorporation of [ 14C]amino acids into protein was studied in homologous cell sap-microsomal or -ribosomal systems. The sedimentation patterns of polyribosomes from Celite-injected and normal rats were similar, while amino acid incorporation into protein per polysomal unit was enhanced after Celite injection. Molecular sieving of cell sap through Sephadex G-25 abolished the differences in activity of ribosomal preparations almost completely, provided the system was supplemented with a mixture of amino acids and GTP. In microsomal systems the differences originally obtained were decreased after molecular sieving of cell sap and microsomes but could not be abolished completely. In the presence of Sephadex-treated cell sap and GTP, the poly U directed incorporation of [ 14C]phenylalanine per particulate RNA was similar in the ribosomal as well as in the microsomal preparations of normal and Celite-injected rats. The results indicate that the originally observed differences in amino acid incorporating activity between normal and Celite-injected rats can be eliminated by various treatments of the subcellular fractions. These treatments result in an increase rather than a decrease of the original ability to incorporate [ 14C]amino acids into proteins.