Chromatographic behavior of selenoproteins in rat serum detected by inductively coupled plasma mass spectrometry.

Two major selenoproteins are present in mammalian serum: extracellular glutathione peroxidase (eGPx) and selenoprotein P (Sel P). The chromatographic behaviors of the two serum selenoproteins were compared in four rodent species, and the selenoproteins in rat serum were identified by measuring enzyme activity and Western blotting. The selenoproteins in rat serum showed a specific chromatographic behavior. In particular, rat eGPx was eluted faster than eGPxs of the other rodent species, although the amino-acid sequences of the rodent species were identical. The elution profiles of Se in rat serum obtained by inductively coupled plasma tandem mass spectrometry (ICP-MS-MS) and ICP-MS were compared. The tandem quadrupoles and the O2 reaction/collision gas completely removed severe interferences with the Se speciation originating from the plasma source and the biological sample matrix. ICP-MS-MS under the O2 mass shift mode gave us more accurate abundance ratios of Se than ICP-MS.

Distribution and metabolism of selenite and selenomethionine in the Japanese quail.

Compared to the many studies on the physiological and toxicological effects of selenium (Se) in mammals, avian Se metabolism is still an unexplored topic. Some birds are useful as poultry for human nutrition. Moreover, birds belong to higher trophic levels in the biosphere and thus may play an important role in Se circulation in the ecosystem in the same way as mammals do. In this study, we analyzed the distribution and metabolism of Se in an experimental bird, the Japanese quail, which was fed drinking water containing sodium selenite or selenomethionine (SeMet). The highest concentration of Se was detected in the pancreas, followed by down feathers, liver, and kidneys. SeMet was more efficiently incorporated into the quail than selenite. The specific and preferable distribution of Se to the high molecular weight fraction in the serum of the quail was observed only in the SeMet-ingestion group. As in mammals, selenosugar and trimethylselenonium were the major metabolites in quail excreta. Three unknown Se metabolites were detected by HPLC-ICP-MS. Although part of the metabolic pathway of Se in the Japanese quail fed selenite and SeMet was the same as that observed in mammals, the bird also showed certain avian-specific metabolic process for Se.