Use of enriched 74Se and 77Se in combination with isotope pattern deconvolution to differentiate and determine endogenous and supplemented selenium in lactating rats

Abstract

A quantitative methodology has been developed to differentiate between endogenous and supplemented selenium in lactating rats using two enriched selenium isotopes. Lactating rats were fed for 2 weeks with formula milk containing one enriched Se isotope, (77)Se, as the metabolic tracer. The isotopic composition of selenium in serum and urine samples was then measured by collision cell ICP-MS after the addition of a solution containing another enriched isotope, (74)Se, as quantitation tracer, before analysis. Isotope pattern deconvolution allowed the transformation of measured Se isotopic abundances into concentrations of natural abundance (endogenous) selenium and enriched (77)Se (supplemented) present in the samples. The proposed methodology was validated using serum and urine reference materials spiked with both (77)Se and (74)Se. The obtained results are discussed in terms of selenium exchange and half-life in lactating rats (11-12 days) and selenium levels in serum in comparison with non-supplemented rats and control rats after maternal feeding.

Elemental and molecular mass spectrometry for integrated selenosugar speciation in liver and kidney tissues of maternal feeding and supplemented rats

“…The selenium isotopes were measured by ICP-MS in the digested samples and the concentrations of natural selenium (reference value) and exogenous Se (spiked 77 Se) were determined from the selenium isotope composition measured in the sample by applying the IPD methodology. 18,19 Table 2 shows the observed quantitative determination values of selenium in the bovine liver reference material for both natural Se (certied value) and for 77 Se (tracer) obtained, which agreed well with the certied Se (natural Se) and the added 77 Se (tracer). Next, the IPD approach was conducted to investigate natural and supplemented total selenium quantication in rat liver and kidneys, as follows: nine livers and eighteen kidneys from nine rats (classied as maternal feeding, non-supplemented and supplemented groups, 3 rats per group) were treated as indicated in the Experimental section.…”

“…The experimental treatments performed were previously described by González-Iglesias et al 18,19,26 In brief, twoweek-old Wistar rats were maintained in metabolic cages (three rats/cage) at 22 C with a light/dark cycle of 12/12 h for two weeks. Rats were then randomized into 3 groups (3 rats per group).…”

The Stoichiometric Transition from Zn6Cu1-Metallothionein to Zn7-Metallothionein Underlies the Up-regulation of Metallothionein (MT) Expression

“…The enriched stable isotopes 34 S, 65 Cu, and 111 Cd contained in a solution at standardized concentration were added after the chromatographic separation (for quantitative speciation). The continuous measurement of the corresponding isotope ratios 32 S/ 34 S, 63 Cu/ 65 Cu, and 114 Cd/ 111 Cd in the ICP-MS allowed us to obtain the "mass flow chromatogram" after applying the isotope dilution equation application (29).…”

“…This is a chemometric technique based on multiple least squares for isolating distinct isotope signatures from mixtures of natural abundances and enriched tracers (33). This mathematical tool, in connection with ICP-MS and stable isotopes, has already been applied for the quantification of selenium and iron (34,35) and sulfur-containing biomolecules (32) and finding distribution of zinc in navy beans (36 …”

A New Tool Based on the Use of Stable Isotopes and Isotope Pattern Deconvolution (IPD)‐ICP‐MS for Nutritional and Clinical Studies

“…In fact, it does not require a calibration set because isotope abundances are independent of concentration. The methodology has been applied to study endogenous and exogenous Se in lactating rats by using 77 Se as metabolic tracer and 74 Se for isotope dilution quantification [34,35]. Furthermore, IPD in connection with stable isotopes has proved to be an important tool in nutritional and clinical studies.…”