Alterations in the length of jejunal villi in mice irradiated with graded doses of X rays.

The length of villi protruding into the jejunal lumen influences the absorptive surface involved in digestion. Since it is an important functional end-point, a correlation between the X-ray dose applied and the average length of jejunal villi was investigated, with the possibility of using it as a radiobiological test system. Mice were given whole-body irradiation in the low- (4-7 Gy) or high-dose (9-12 Gy) range in a single fraction. Villus length was measured in arbitrary units from stained histological sections. It was found that villus length was affected by both the dose ranges used, but the effect observed in the low-dose range was not dose-related, whereas in the high-dose range there was a correlation between the radiation dose applied and the reduction in the average length of villi. Therefore, it is not suitable as an assay for low doses and for high doses there is already a test system (the microcolony survival assay) which is more practical and widely used. Factors which may influence villus length as well as the basic mechanisms involved are reviewed briefly. Experimental data presented indicate that the villus length may also be dependent on the number of crypts per jejunal circumference.