THE EFFECTS OF INCORPORATED CERIUM-144 ON THE FERTILITY OF MICE AND THE DEVELOPMENT OF THEIR OFFSPRING

The state of parent mice injected with radioactive cerium and the state of their offspring; reproducibility of control parent mice and their offspring; the amount of radioactivity transmitted to the offspring and the offspring's sensitivity to radiation were studied. White laboratory mice of both sexes aged 2-2.5 months were injected intraabdominally with 0.25 ml of a solution containing cerium-144 in doses of 0.5 or 1.25 mu c/g of the animal's weight- (LD/sub 50// 160/ and LD/sub 50//80 respectively). The offspring's sensitivity to irradiation from a Co/sup 60/ source was also studled when the offspring were aged 3 months (irradiated in a dose of 600 r) and 4 months (700 r). It was found that 0.02 -- 0.03% of the cerium incorporated in the parent mice 2-3 weeks before the onset of pregnancy was transmitted to the offspring. The increase in weight of the parent mice in the series lagged behind that of the control animals, but the offspring from the test mice developed at the same rate as the control animals. The administration of cerium in a dose of 0.5 mu c/g 2 weeks before the mice were paired had no effect on their fertility. With a greater period betweenmore » incorporatlon of the cerium and pairing of the animals, the fertility of the females dropped, while the fertility of the males remained normal. Incorporation of the cerium in a dose of 1.25 mu c/g 3 weeks before pairing reduced the fertility of both females and males, although the females proved more sensitive to radiation. The average number of mice per litter at various stages after introduction of the cerium in doses of 0.5 or 1.25 mu c/g did not differ from the control animals. The fertility of the first generation of mice obtained from mice injected wlth 0.5 mu c/g of cerium was the same as the fertility of the control animals. Offspring obtained from various combinations of crossing tests (0.5 mu c/g) and control mice proved more resistant to irradiation with Co/sup 60/. Moreover, the females were more resistant to radlation than were the males. Resistance to radiation persisted for a long period of time. It was found that large amounts of radioactivity are trans mitted to the embryo via the placenta only in cases where the radioactive agent is administered to the body of the female during pregnancy. If the radioactive agent is incorporated a few days before the start of pregnancy, very lit tle of it passes into the embryo. Cerium was incorporated in the females 2-3 weeks before the onset of pregnancy, due to which only an insignificant proportion of the cerium was transmitted from the mother to the offspring. Offspring from females injected with cerium had a higher resistance to radioactivity due to their previous irradiation in the embryonic stage. (OTS)« less