Continuous Low-Dose Radiation Effects on Successive Litters of the Albino Rat

Groups of 10 mature female rats of the Holtzman strain were exposed continuously to gamma radiation levels of 0, 2, 5, 10, and 20 r daily after conception. There were no essential differences in litter size, or in number of offspring born, between four successive litters produced while the mothers remained continuously in the gamma radiation field. There was no significant variation in the first six litters born at the 0-r, 2-r, 5-r, and 10-r daily radiation levels; however, at 20 r daily only one offspring was born in the fifth litter, and none in the sixth. No anomalies were observed at any level of the radiation used in these experiments, except for a slight decrease in average weight of the newborn. Offspring from the third litter born to mothers continuously in the radiation chamber were shown to be fertile in those groups which received 0, 2, and 5 r of gamma radiation administered over a 23-hour period daily. The corresponding animals receiving daily doses of 10 and 20 r from the time of conception were sterile when bred together or with known fertile unirradiated males.