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.