Dose Dependence and Sequential Changes in Mouse Small Intestinal Weight Induced by Ionizing Radiation. ∗

Summary

The effect of 2000 KVP X-ray and gamma (CO⁶⁰) irradiation on the weights of the small intestine of C. F. and white Swiss mice was presented. Weight loss in the small intestine showed dose dependence when measured 2 days postirradiation with doses of 150-950 r. Doses above 950 r showed no further weight loss at 2 days resulting in a plateau effect. It was pointed out that under properly controlled conditions, this technic may be used as a biological dosimeter in determining dosage or rem, relative biological effectiveness of various types of radiation, strain and species differences in response, effects of protective agents, and the relative sensitivity of the gastrointestinal tract compared to other tissues. Sequential weight changes in the small intestine were studied after various times and doses of gamma radiation in white Swiss mice. Radiation was followed by rapid weight loss in the gut (dose dependent) reaching a maximum by the 2nd or 3rd day followed by recovery above the control range at 3 to 5 days. The magnitude of this peak recovery tended to increase with dose up to 750 r and to be somewhat delayed with increasing dose. These findings showed correlation with similar time and dose studies on mitotic inhibition of the mouse small bowel epithelium (7). By the 7th day the intestines returned to the control range and remained in the range with doses through 550 r. However with doses above 550 a secondary depression in gut weight occurred which was manifest on the 10th and 12th postirradiation days.