The glucose effect and cortisone action upon rat liver metabolism

1. 1. A single oral glucose load in normal, fasted rats effected a very early, transient increase of the level of liver tyrosine transaminase activity. Afterwards the enzyme activity was strongly depressed for at least 16 h, thus corresponding to the well-known “glucose effect” in mammals. Glycerol and fructose had similar inhibitory effects; but mannose and galactose were ineffective; ribose and galactosamine enhanced the tyrosine transaminase level. The glucose load was no longer effective in streptozotocin-diabetic rats. 2. 2. Data presented favor an alteration in the enzyme protein synthesis as the mechanism for the “glucose effect” rather than a mere inhibition of its activity. 3. 3. When administered together with cortisone, glucose strongly altered tyrosine transaminase induction and most of the early parameters of the glucocorticoid action. 4. 4. Glucose effect was largely relieved by simultaneous administration of glucagon thus indicating that the liver adenyl cyclase system might be involved. 5. 5. It is suggested that the nutritional state of the organism could modulate, in an as yet unknown manner, the hepatic biochemical responses to cortisone administration.