Effects of irradiation on the release and retention of labelled DNA in the small intestine of mice.

Mice were whole-body irradiated with 300, 500 and 800 rd (60Co) one hour or three days after administration of 3H-thymidine. The time courses of the total and specific activity of DNA indicate that three days after exposure with 500 and 800 rd the mitotically active cells were selectively lost from the small intestine. The release of labelled DNA was determined in the fraction of DNA soluble in 0.14 N NaCl. The results suggest that the relatively small fraction of soluble DNA belongs to the mitotically active cells probably having died in the interphase.