Caesium retention during pregnancy in mice

The effect of pregnancy on caesium retention in mice was assessed. Fifteen female mice were injected with caesium-137 solution intraperitoneally and m easurements of body radioactivity were performed. For the control group of mice (n = 8), caesium retention could be adequately described, for the time period from day T = 7 to 26 post-injection, by a two exponential model, wh ere 90% of caesium was eliminated by a component with a biological half-tim e of (2.83 +/- 0.78)d and 10% by a component with a biological half-time of (16.3 +/- 7.3) d. However, an alteration of caesium elimination rate, whic h affects the component with the longer half-time was observed in the group of pregnant mice (n = 7). The observed effect was a decrease in excretion rate, in contrast to recent human observations where an increase was found. This difference in mice is associated with changes in metabolic rate, and, to a first approximation, is related to the gain in mass during pregnancy. (C) 1999 Elsevier Science Ltd. All rights reserved.