The effects of continuous low level irradiation on reproduction of albino rats exposed during late prenatal and early postnatal development periods

A study was conducted to obtain data on effects of chronic radiation at levels of 1, 2, 5, 10, 20, and 40r per day for a total dose of 30, 60, 150, 300, 600, and 1200r respectively on Holtzman strain offspring irradiated for 30 days beginning on the 15th day pf gestation. A commercial pelleted ration (Purina Lab Chow) and water were supplied ad libitum to all animals throughout the experiment. A mean temperature of 80° and a 12 hour light-dark cycle in both the radiation chamber and colony room were maintained. All animals were housed in wire mesh cages, with efforts made to retain a high-standard of cleanliness to prevent epidemics and to promote survival of all treatment groups. There were no apparent real effects from continuous radiation to the dams which produced offspring at treatment levels of 0, 1, 2, 5, 10, 20, and 40r per day with no regards to the number of females littering and average litter size produced. Birth weights were significantly decreased (P< .05) in groups receiving 20 and 40r per day as compared with non-irradiated controls: Body weights at birth, 14, 23, and 300 days of age were significantly depressed in the group receiving 40r per day as compared with non-irradiated controls. There were no differences in body weights of the other treatment groups after 125 days of age as compares with normal controls. At 65, 170, and 300 days of age, a high percentage of animals receiving 1, 2 and 5r per day for a total dose of 30, 60, and 150 r respectively were, or would have been, fertile when compared with non-irradiated controls. Sires which had received 10, 20, and 40r per day did not produce any litters when mated with known fertile females. Histological examination of the testes of the 10, 20, and 40r per day groups shows only a few tubules containing active germinal epithelium, which would account for the absence of litters. The combined data obtained on the fertility, vaginal plug, mating activity, and histological observations demonstrated that a total dose of 300, 600, and 1200r at the rate of 10, 20, and 40r per day for 30 days (beginning on the 15th day of gestation) produced complete sterility, with the exception of one animal at the 300r level.