DISTRIBUTION OF 137Cs IN RAT TISSUES AFTER VARIOUS SCHEDULES OF CHRONIC INGESTION

The aim of this work was to compare the distribution of 137 Cs in organisms after chronic ingestion following different schedules. Rats were contaminated through drinking water containing 6,500 Bq L -1 of 137 Cs, starting either at birth, at weaning, or upon reaching adult age (13 wk). Animals were then sacrificed after different durations of ingestion. 137 Cs content of organs and excreta were determined by γ counting. A slight decrease in 137 Cs elimination through urine was observed according to the age of animals. All organs tested showed similar 137 Cs content, with the exception of striated muscles and the thyroid at certain ages, which showed the highest accumulation of 137 Cs. The lowest 137 Cs concentration was found in the blood, which acts as a transfer compartment after absorption in the intestine. Substructures of the central nervous system showed a homogeneous level of 137 Cs accumulation, except for the olfactive bulbs. In these structures, an increased concentration of 137 Cs was observed, suggesting a possible direct route of intake through the nasal epithelium. Overall, these results are in agreement with current models for the biokinetics of 137 Cs. However, these results also suggest that the thyroid should be taken into amount in future models of 137 Cs biokinetics.