Effect of X-irradiation on hepatic carbohydrate enzymes in control and hypophysectomized rats

¹ Montreal Cancer Institute, Research Laboratories, Notre Dame Hospital and University of Montreal, Montreal, Canada

The sequence of metabolic events was investigated in rats for 8 days after exposure to 600 r total-body x-irradiation. The preirradiation studies showed that in hypophysectomized animals 18 hours of fasting reduced the activities of enzymes involved in glucose-6-phosphate utilization indicating that the hypophysis is involved in the physiological maintenance of these enzymatic activities. In control animals after irradiation fasting blood sugar and liver glycogen increased reaching a peak at 3 days and returning to normal range at 8 days postirradiation. Hepatic phosphohexoseisomerase and phosphoglucomutase activities indicated the presence of an increased glycogenesis and gluconeogenesis. Liver 6-phosphogluconate dehydrogenase activity increased to almost double the preirradiation value and stayed at this level during the whole postirradiation period. Glucose-6-phosphatase activity was not affected by irradiation. In hypophysectomized animals after irradiation blood sugar, liver glycogen and most enzymatic activities remained essentially in the preirradiation level, indicating that hypophysectomy abolished the characteristic carbohydrate metabolic response to radiation. The deficient metabolic reaction of hypophysectomized animals was correlated with the increased mortality rate in this group.