Intestinal peptidase activity following whole-body irradiation in mice

Dipeptidase activity (Gly-L-Leucine, L. Leu-Glycine, Gly-L-Phe, L Phe-Gly) was measured in the cytoplasmic fraction of the small bowel mucosa of mice eating three synthetic, defined formula, diets or Purina Chow. The activity/milligram protein of all peptidases was found to be reduced seven days after the last of six weekly exposures to 400 rads (Cobalt 60). The magnitude of reduction varied from half the control value for L-Leu-Glycine peptidase to between one fourth and one fifth the control values for the other three peptidases. These findings may partly explain the improved tolerance to radiation in mice eating a diet containing amino acids (protein hydrolysate) instead of whole protein.