Relation of hepatic ketogenesis to radiation-induced decrease in fasting ketonemia.

Abstract

Male, weanling rats were exposed to 500 r of whole-body x-irradiation and then fasted. Control rats were concurrently fasted. Ketonemia, ketonuria, hepatic glycogen, ketogenesis by liver slices and fatty acid oxidase activity of liver mitochondria were measured. A radiation-induced decrease in fasting ketonemia was observed. This decrease was mainly in the ß-hydroxybutyric acid fraction. Ketonuria was similar in both control and irradiated lots the 1st postirradiation day and lower in the irradiated lot during the 2nd day. Decreased ketonemia in the irradiated rats, which exhibited diuresis, was thus apparently not due to increased urinary excretion of ketone bodies. Ketogenesis by liver slices from irradiated rats was depressed. This indicated that an antiketogenic process contributed to the radiation-induced decrease in fasting ketonemia. Fatty acid oxidase activity of liver mitochondria isolated from control and irradiated rats was similar. Thus, rate-limiting fatty acid oxidizing enzymes were not altered by radiation under these conditions. This illustrates an apparent modifying effect of other cellular fractions on fatty acid oxidation in mitochondria.