Radiation-induced DNA strand breaks and their repair in the developing rat brain.

Rats, 5, 10 or 25 days old, were 60 Co gamma irradiated. The induction of DNA strand breaks was studied after killing the rats within 1 min after irradiation, and the repair of the induced breaks after various intervals up to 180 min. Cell suspensions were prepared from the brain and samples were transferred into alkaline solutions. The fraction of DNA remaining double-stranded after 30 min alkali treatment was estimated after separation of single- and double-stranded DNA on hydroxylapatite. The amount of DNA strand breaks induced per Gray (1--8 Gray) was found to be in accordance with earlier in vivo studies of the mouse small intestine and mouse spleen. The DNA strand breaks in the rat brain induced by 4 Gray 60Co gamma irradiation were repaired 30 min after irradiation in all age groups studied.