241Am Distribution and Retention in Pregnant Mice, in their Offspring and in Non-Pregnant Mice: Comparison Between Continuous Am Administration and Single Injection

Abstract

Pregnant BALB/c mice and age and sex matched nulliparous controls were contaminated with 241Am (13 kBq per mouse) by two different procedures: (1) a single intraperitoneal injection at the 14th day of gestation, and (2) continuous adminstration between the 7th and 14th day of gestation and between the 14th and 19th day of gestation. Continuous administration was achieved by implanting osmotic pumps filled with 241Am which released the 241Am activity at a constant rate. Five days after the termination of contamination, 241Am incorporation was measured in the tissues of adults and in the liver and the femur of newborn and one-month-old mice. Pregnancy results in higher 241Am concentrations in bone but lower concentrations in the liver of the mothers. Protracted administration of 241Am compared to a single injection resulted in a lower concentration of 241Am in the livers of pregnant mice, their nulliparous controls and from newborn mice. The higher 241Am concentration in the femur at birth after protracted exposure before 14 days of gestation compared to protracted exposure after 14 days of gestation could reflect the increased placental transfer of 241Am with advancing gestational age. Radiation doses to the femur were estimated between 4 and 20 mGy. Haemopoietic changes were noticed at these dose levels in all groups until at least 6 months after birth.