Dipeptidase activity in the small intestine after irradiation at different times of the day.

The behaviour of leucinaminopeptidase, an intestinal epithelium brush border enzyme, was investigated to find out whether the same irradiation does administered at different times of the day would induce differentiated modifications. Three activity phases were evidenced: increase, reduction during acute damage, and recovery. The results showed that the general behaviour in the four irradiated groups was similar, although some differences were observed mostly regarding the outset of the initial increase and the recovery. The time of irradiation affects the behaviour of the enzyme activities which show circadian oscillations. The results seem to show a quicker tendency to a return to normal values in the group irradiated at the end of the darkness period.