Metabolic tracer studies selenium

Numerous trace elements are known to be nutritionally essential in man In order to assess the essentiality, dietary availability, and metabolic fate of these, means of labeling for subsequent identification are needed In animal studies, radioisotopes are often used for this purpose, but their use in human studies is generally contraindicated due to the radiation hazards An alternate method is to use stable isotopes of the elements, which overcomes this limitation A method will be described for conveniently measuring the stable isotopes of selenium, permitting their use as metabolic tags in tracer studies Using one stable isotope as the tracer and another as internal standard, one can quantitatively identify in a sample the tracer, natural (unenriched) selenium present with it, and total selenium Some of the kinds of information obtainable from metabolic tracer studies will be discussed ... 

Stable Isotopes of selenium (as well as those of other elements) can provide a means of addressing these questions by their employment In metabolic tracer studies The same Information can be obtained as when employing radiotracers In animal studies, but without the associated radiation hazards In human studies For example, stable Isotopes of selenium can be biologically Incorporated Into test foods and these used to monitor selenium bloavallablllty (6,7) ... 

Total Selenium As mentioned earlier, stable isotope dilution is a powerful tool in trace element analysis. Let us first look at how it can be used to determine the total selenium content of a sample. In the following section we will develop the method further for stable isotopes in metabolic tracer studies. 

Tracer Studies. In addition to using as an Internal standard as described above, a second enriched Isotope of selenium can be used as a metabolic tag. Let us take as an example the use of enriched as a tracer. We have used a batch of 76se for this purpose, with the relative abundances shown in Table III. 

We can extend this concept to tracer studies in humans as well Let us take as an example the metabolic study of Swanson et al ( ) In this study, 3 groups of women (non-pregnant, early-pregnant and late-pregnant) were placed on a controlled diet containing 150 ug Se/day On day 8, they also ingested 150 ug Se, but 110 ug of it was natural (unenrlched) selenium and 40 ug of it was enriched 630 incorporated into egg products (7). 

Vandael, P. (2004) Stable isotope-enriched selenite and selenate tracers for human metabolic studies a fast and accurate method for their preparation from elemental selenium and their identification and quantification using hydride generation atomic absorption spectrometry. 

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