Biokinetics of 90Sr after chronic ingestion in a juvenile and adult mouse model

Abstract

The aim of our study was to define the biokinetics of (90)Sr after chronic contamination by ingestion using a juvenile and adult murine model. Animals ingested (90)Sr by drinking water containing 20 kBq l(-1) of (90)Sr. For the juvenile model, parents received (90)Sr before mating and their offspring were killed between birth and 20 weeks of ingestion. For the adult model, (90)Sr ingestion started at 9 weeks of age and they were killed after different ingestion periods up to 20 weeks. The body weight, food and water consumption of the animals were monitored on a weekly basis. Before killing and sampling of organs, animals were put in metabolic cages. (90)Sr in organs and excreta was determined by liquid scintillation β counting. Highest (90)Sr contents were found in bones and were generally higher in females than in males, and (90)Sr retention varied according to the skeletal sites. An accumulation of (90)Sr in the bones was observed over time for both models, with a plateau level at adult age for the juvenile model. The highest rate of (90)Sr accumulation in bones was observed in early life of offspring, i.e. before the age of 6 weeks. With the exception of the digestive tract, (90)Sr was below the detection limit in all other organs sampled. Overall, our results confirm that (90)Sr mainly accumulates in bones. Furthermore, our results indicate that there are gender- and age-dependent differences in the distribution of (90)Sr after low-dose chronic ingestion in the mouse model. These results provide the basis for future studies on possible non-cancerous effects during chronic, long-term exposure to (90)Sr through ingestion in a mouse model, especially on the immune and hematopoietic systems.

Chronic exposure to low concentrations of strontium 90 affects bone physiology but not the hematopoietic system in mice

“…). This was consistent with a previous study showing that the ratio of 90 Sr accumulation in bone is overall higher in females as compared with males (Synhaeve et al ., ).…”

“…90 Sr accumulated mainly before the age of 6 weeks, that is, during bone growth. These results are consistent with a previous study on the biokinetics of 90 Sr with the use of the same mouse model (Synhaeve et al ., ) and give rise to a whole body absorbed dose between 0.3 mGy at birth and 10 mGy at 20 weeks depending on the age of animals, as previously estimated (Bertho et al ., ).…”

“…Based upon an assumed daily water consumption of 4 ml per animal per day at adult age (Synhaeve et al, 2011), a 90 Sr ingestion of about 80 Bq per animal per day at adult age was expected, corresponding to 0.94 ng of total Sr (stable + radioactive) per animal and per day. 90 Sr ingestion was monitored though measurement of water consumption and internal contamination of animals was verified by measurement of 90 Sr in femurs of sacrificed animals as previously described (Synhaeve et al, 2011). Male and female parents received normal or 90 Sr-containing water starting two weeks before mating and until their date of sacrifice.…”

“…Femurs were either frozen in liquid nitrogen for gene expression analysis, or decalcified (RDC, CML, France) and fixed in 4% formaldehyde for histological analysis or flushed to collect hematopoietic cells. A tibia or a femur from each animal was used in order to measure 90 Sr concentration in bones, as previously described (Synhaeve et al, 2011).…”

“…We thus used our mouse model of chronic contamination through drinking water with a 90 Sr concentration of 20 kBq l −1 . Previous studies showed that this concentration led to a daily ingestion of 80–100 Bq per day and per animal (Bertho et al ., ; Synhaeve et al ., ), and give rise to whole body radiation dose of 10 mGy by the end of the 20 week study period (Bertho et al ., ). In this model, we study various parameters in order to delineate possible effects of 90 Sr chronic ingestion on two physiological systems, the hematopoiesis and bone physiology.…”