Circadian changes of gluconeogenic enzymes in irradiated rats

The effect was studied of whole-body irradiation at different times of the day on the circadian rhythms of gluconeogenic enzymes. It was found that: 1. liver and kidney enzyme activities were highest in daylight and lowest in the middle of the hight; 2. the 12/h circadian rhythm of glucose-6-phosphatase and fructose-1,6-bisphosphatase activities in the liver and the renal cortex followed a similar course; 3. a lethal whole-body dose of 14.4 Gy of X-rays did not affect the circadian oscillation curves of the given enzymes, with the exception of fructose-1,6-bisphosphatase in the liver of irradiated rats, where the rhythm was lost. (author)