Abstract
High dose exposure to radiation causes gastrointestinal tract (GIT) injuries. GIT injury is one of serious problems in accidental exposure to high dose radiation and also in radiation therapy. However, the mechanism(s) is not fully understood and its treatment is unknown. Stem cells in crypt differentiate into mature cells and migrate upward from the base of the crypt toward the villus tip. Differentiated cells rapidly lose their proliferative ability and then undergo apoptosis. In order to study the mechanisms of GIT injury by radiation, we investigated that effect of radiation on protein expression of mouse intestinal epithelial cells along the crypt-villus axis. Epithelial cells were sequentially isolated cells from the villus tip to the crypts of mouse small intestine by the Mariadason method. We compared levels of protein by western blot analysis. Expression of proliferating cell nuclear antigen (PCNA) and Bax was expressed in the crypt and their levels were reduced toward the villus axis. On the other hand, the expression of active form of caspase 3 was accumulated in cells of the villus tip. Radiation reduced levels of PCNA. Radiation increased levels of Bax and activated caspase 3 in the crypt but not in the villus tip. The p21 protein was not detected in intestinal epithelial cells. However, radiation increased the level in cells toward the crypt. Our results suggest that the cell proliferation and response to radiation is differently regulated in the crypt from the villus.
