Selenium distribution and metabolic profile in relation to nutritional selenium status in rats

The disposition of selenium (Se) was investigated in Wistar rats of various Se status after an intravenous injection of 82Se-selenite. Various fractions of plasma, urine, and cytosols from liver and kidney were separated by high performance liquid chromatography (HPLC), coupled with an inductively coupled argon plasma-mass spectrometry (ICP-MS). The technique allowed simultaneous differentiation of the fate of injected and endogenous Se, and if it was influenced by the previous Se burden in the tissues. A broad Se-peak from plasma was resolved in two fractions by assessing the m/z 82/78 ratios. Urinary profiles indicated that the metabolism of Se was dose-dependent; monomethylselenol being the primary metabolite of Se in untreated animals, whereas noticeable amount of trimethylselenonium ion was detected after the injection of 82Se. Liver and kidney cytosols contained complex Se-enriched fractions, a positive identification of which was not done in this study. In most cases, the enrichment of tissue fractions with the stable isotope was altered by the dietary Se levels, the isotope nevertheless was exchanged with the endogenous Se in various macromolecules to a varying degree.