The effect of cortisone on protein breakdown and synthesis in rat skeletal muscle

The effect of cortisone administration on the rates of muscle protein breakdown and synthesis has been studied in the rat extensor digitorum longus muscle. Cortisone acetate (100 mg/kg body weight/day) was administered intraperitoneally for 1--3 days. Muscle wieght and protein content were significantly reduced by cortisone administration. Rates of protein breakdown were measured by tyrosine release from the isolated muscle into the intracellular pool and medium during a 2-h incubation with cycloheximide to block protein synthesis. Rates of protein synthesis were assayed by [14C]tyrosine incorporation into protein of the isolated muscle during a 2-h incubation. Cortisone administration inhibited significantly the rate of protein synthesis after 1--3 days treatment and also reduced significantly the rate of protein breakdown per muscle after 3 days treatment. The synthesis of myofibrillar and soluble proteins was affected to the same extent. These results strongly suggest that the effect of cortisone administration on muscle protein is mainly through its inhibition of protein synthesis rather than through an acceleration of protein breakdown.

Effect of triamcinolone administration on content of flavins in rabbit liver

Triamcinoline acetonide (10 mg per kg of body weight a day) was administered to rabbit fed on a laboratory chow diet. The content of flavins in liver but not in kidney, muscle and brain started to decrease 24 h after a single dose. The activities of enzymes in the liver were determined: the activities of pyruvate dehydrogenase complex, lipoamide dehydrogenase (NADH:lipoamide oxidoreductase EC 1.6.4.3), NADH dehydrogenase (NADH : (acceptor) oxidoreductase EC 1.6.99.3) and D-amino acid oxidase (D-amino acid: oxygen oxidoreductase (deaminating) EC 1.4.3.3) were decreased but those of succinate dehydrogenase (succinate : (acceptor) oxidoreductase EC 1.3.99.1) and xanthine oxidase (xanthine : oxygen oxidoreductase EC 1.2.3.2) remained unchanged. The activities of enzymes in the kidney, however, remained unchanged except the decrease in the activity of pyruvate dehydrogenase complex.