The effects of the time interval in fractionated X-ray treatment of mouse spermatogonia

Abstract

Male CBA strain mice were submitted to fractionated radiation treatment of spermatogonia. Effects of doses of 300 R + 300 R, 400 R + 400 R and 500 R + 500 R with time intervals of 24, 48, 72 and 144 h between irradiations were studied. Intervals of 24, 48 or 72 h prolonged the post-irradiation sterile period compared with doses given in a single treatment or with an interval of 144 h. This was interpreted as an indication that the shorter intervals led to a greater amount of cell killing. In matings with CBA females all irradiated groups gave higher rates of intrauterine death and lower implantation rates than controls. Differences between irradiated groups within series imply that even the rate of dominant lethals may be increased by application of the dose in fractions. The results lead to the conclusion that time intervals of up to 72 h between irradiation doses may increase the amount of genetic damage compared with the same total dose given as a single treatment.