Hepatic Glycogen, Lipogenesis and Glucose-6-Phosphatase in X-Irradiated and Control Rats

¹ From the Departments of Biochemistry and Radiology, Vanderbilt University School of Medicine, Nashville, Tennessee

Incorporation of C¹⁴-acetate into hepatic fatty acids increased in irradiated, fasted rats (750 r total-body x-irradiation) compared to fasted controls as early as 6 hours postirradiation. At this time hepatic glycogen in irradiated animals was lower than in controls and lower than in irradiated animals at 30 minutes postirradiation. Incorporation remained constant at 12 hours postirradiation but glycogen concentration in irradiated rats was increased over controls. At 18 hours the irradiated rat exhibited both increased hepatic glycogen and increased lipogenesis. The increase in liver glycogen in irradiated, fasted rats could be prevented effectively by administration of S,ß aminoethylisothiouronium bromide 10 minutes prior to irradiation. In those irradiated rats in which symptoms of toxicity of the drug were not severe, enhancement of hepatic lipogenesis either was not prevented or was only partly prevented. The results are consistent with the hypothesis that liver glycogen is not the sole factor contributing to increased hepatic lipogenesis in irradiated fasted rats. Assay for hepatic glucose-6-phosphatase at 0.5, 24 and 48 hours after 750 or 1000 r total-body x-irradiation revealed no significant change due to the irradiation. However, both concentration and total activity of the enzyme were increased by fasting.