Rat hepatic lysine-2-oxoglutarate reductase activity. Induction by lysine, glucagon and cycloheximide administration

The activity of hepatic lysine-2-oxoglutarate reductase was determined in white female rats maintained on one of two dietary lysine levels (0.23 and 0.54% in diets A and B, respectively). The high dietary lysine increased the enzyme activity (p less than 0.05) twofold compared with the activity obtained with the diet A (67 vs. 27 mumol saccharopine/30 min/g liver protein). Repeated intraperitoneal injection of glucagon (259 microgram/100 g body weight/day) showed a short initial drop in the enzyme activity, followed by a marked rise, which remained above the basal level after withdrawal of the drug. Repeated injections of cycloheximide increased the enzyme activity, and the findings suggested that the apparent increase was due to the inhibition of the system responsible for the degradation of the enzyme. The individual free amino acids of the livers varied as a function of treatment. The ratio of E/N amino acids was found to be a good measure of the physiological condition of the animal, with the lowest value in animals treated with cycloheximide.