Radiation-induced DNA strand breaks and their rejoining in crypt and villous cells of the small intestine of the mouse

A sensitive method has been developed for the estimation of DNA strand breaks in the proliferating crypt cells and the differentiated villous cells of the small intestine of the mouse. The method is based on the observation that the rate of denaturation of DNA to single strands in alkali is increased after irradiation, the interpretation being that this effect is due to DNA strand breaks. Various tests and developments of the method, when applied to an in vivo situation, have been made. Using whole-body 60Co gamma irradiation (300 to 2000 rad), the yield of breaks induced per rad and the kinetics of their rejoining in vivo were found to be very similar in the crypt and villous cells. Most DNA strand breaks seemed to be rejoined within 30 min. In contrast with these findings, the crypt and villous cells have very different radiosensitivities when histological criteria are used to estimate, for example, cell death. This difference in radiosensitivity thus seems to be unrelated to the capacity of the cells to rejoin the main fraction of radiation-induced single strand breaks in DNA