ALPHA-PARTICLE IRRADIATION OF HEMATOPOIETIC-TISSUE IN PRENATAL AND POSTNATAL MICE .1. DISTRIBUTION OF PU-239 AFTER MIDTERM CONTAMINATION

Pregnant mice (at 13 days gestation) and age-matched controls were injected with 30 kBq Pu-239/kg and the distribution of plutonium in maternal and foetal tissues measured. Approximately 2% of the activity injected into the mother reached each foetus in 24h, 95% of which was contained in membranes and placenta. The concentration of plutonium in foetal liver was 3 times the average foetal body concentration; both liver and body concentrations in the foetus increased by the end of gestation. Each pup accumulated only 0.01% extra injected activity after 9 days lactation and, as the resulting concentrations in the neonatal skeletion were low, we conclude that the greatest haemopoietic risk to the offspring from mid-term contamination in utero is in the foetal liver (which received an average dose of 10-14 mGy between the time of mid-term contamination and birth). By the end of gestation about one-quarter of the original activity was transferred to foetal tissues from the maternal liver and skeleton. No significant changes in maternal distribution were detected as a result of lactation. The results of this study are discussed, along with a compilation of previously published data.