The kinetics of 75Se-selenium in relation to dose and mode of administration to mice

To investigate the effect of selenium in relation to different environmental conditions a study on the kinetics of the element in mice has been carried out on 54 female mice. 75Se (selenite) was administered as a single dose or continuously through drinking water. Different dosage levels were used ranging from "tracer dose" to subtoxic doses. Wholebody counts revealed a biphasic elimination. The first rapid phase was strongly dose-dependent, while the slower second phase of elimination appeared independent of dose as well as mode of administration with a biological half-life of 14.4 +/- 3.2 days. Liver, blood, kidney and lungs were found to contain most of the selenium, here also a two-phased elimination was observed. The biological half-lives for elimination calculated during the second phase gave a mean of 10.7 days with a range of 8.7 to 12.5 days. With continuous administration through drinking water a steady state was obtained after 300 to 400 hours of administration according to concentration. A linearity between amount retained at steady state and log concentration in drinking water is indicated. The results on biological half-lives are discussed in relation to previous publications.