Age-Dependent Uptake and Retention of 239Pu: Its Relationship to Haemopoietic Damage

Abstract

239Pu was administered intravenously to pregnant (30 Bq.g-1 at 4 or 13 d gestation), intraperitoneally to neonatal (10 Bq.g-1) or intravenously to weanling (30 Bq.g-1) mice and its uptake, transfer and retention in various tissues of the mother and her offspring measured. The amount given to the neonates was the same as that retained at birth following transplacental uptake from a mother contaminated at 13 d gestation. Of the 1000 Bq 239Pu given at 13 d gestation, less than 2 Bq (calculated to give an average radiation dose of only 10-14 mGy over the period from injection to birth) was found in the liver of offspring at birth and only 0.1 Bq in the femur. There was about 90 times less 239Pu in the neonates when plutonium was injected at 4 d gestation and about 500 times less than in their mothers. The direct injection to neonates or weanlings resulted in higher femoral plutonium concentrations than by indirect transplacental routes. The resultant 500-fold range in concentration between mice contaminated at 4 d gestation and those contaminated post-natally persisted for at least one year. In spite of higher levels of 239Pu, late contamination resulted in 70% less haemopoietic damage than did early contamination suggesting that embryonic haemopoiesis could be up to 1000-fold more sensitive than post-natal haemopoiesis. Additionally, different mechanisms of inducing this damage operated at different stages.