Accumulation and distribution of uranium in rats after chronic exposure by ingestion
Résumé
Data describing the biokinetics of radionuclides after contamination come mainly from experimental acute exposures of laboratory animals and follow-up of incidental exposures of humans. These data were compiled to form reference models that could be used for dose calculation in humans. In case of protracted exposure, the same models are applied, assuming that they are not modified by the duration of exposure. This work aims at testing this hypothesis. It presents new experimental data on retention of uranium after chronic intake, which are compared to values calculated from a biokinetic model that is based on experiments of acute exposure of rats to uranium. Experiments were performed with 56 male Sprague Dawley rats, from which 35 were exposed during their whole adult life to 40 mg L-1 of uranyl nitrate dissolved in mineral water and 21 were kept as controls. Animals were euthanatized at 32, 95, 186, 312, 368, and 570 d after the beginning of contamination. Urine and all tissues were removed, weighted, mineralized, and then analyzed for uranium content by Kinetics Phosphorescence Analysis (KPA) or by ICP-MS. Experimental data showed that uranium accumulated in most organs, following a nonmonotonous pattern. Peaks of activities were observed at 1-3, 10, and 19 mo after the beginning of exposure. Additionally, accumulation was shown to occur in tissues such as teeth and brain that are not usually described as target organs. Comparison with model prediction showed that the accumulation of uranium in target organs after chronic exposure is overestimated by the use of a model designed for acute exposure. These differences indicate that protracted exposure to uranium may induce changes in biokinetic parameters when compared to acute contamination and that calculation of dose resulting from chronic intake of radionuclides may need specific models that are not currently available. Copyright © 2006 Health Physics Society.
Mots clés
mineral water
uranium
uranyl nitrate
acute toxicity
animal experiment
animal model
animal tissue
article
bioaccumulation
brain
chronic toxicity
comparative study
controlled study
dose calculation
euthanasia
experimental model
ingestion
isotope dilution assay
long term exposure
male
mineralization
nonhuman
phosphorescence
prediction
priority journal
radioactive contamination
radioisotope distribution
rat
rat strain
tissue
tooth
toxicokinetics
urinalysis
weight
animal
biological model
oral drug administration
Sprague Dawley rat
tissue distribution
urine
Animalia
Administration
Oral
Animals
Male
Models
Biological
Rats
Sprague-Dawley
Tissue Distribution
Uranium