Selenium metabolites in human urine after ingestion of selenite, <Emphasis Type="SmallCaps">L</Emphasis>-selenomethionine,or <Emphasis Type="SmallCaps">DL</Emphasis>-selenomethionine: a quantitative case study by HPLC/ICPMS |
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Authors: | Doris?Kuehnelt Norbert?Kienzl Pedro?Traar Nam?Hoang?Le Email author" target="_blank">Kevin?A?FrancesconiEmail author Takafumi?Ochi |
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Institution: | (1) Institute of Chemistry-Analytical Chemistry, Karl-Franzens University Graz, Universitaetsplatz 1, 8010 Graz, Austria;(2) Laboratory of Toxicology, Faculty of Pharmaceutical Sciences, Teikyo University, Sagamiko, 199-0195 Kanagawa, Japan |
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Abstract: | To obtain quantitative information on human metabolism of selenium, we have performed selenium speciation analysis by HPLC/ICPMS
on samples of human urine from one volunteer over a 48-hour period after ingestion of selenium (1.0 mg) as sodium selenite,
L-selenomethionine, or DL-selenomethionine. The three separate experiments were performed in duplicate. Normal background urine from the volunteer
contained total selenium concentrations of 8–30 μg Se/L (n=22) but, depending on the chromatographic conditions, only about 30–70% could be quantified by HPLC/ICPMS. The major species
in background urine were two selenosugars, namely methyl-2-acetamido-2-deoxy-1-seleno-β-D-galactopyranoside (selenosugar 1) and its deacylated analog methyl-2-amino-2-deoxy-1-seleno-β-D-galactopyranoside (selenosugar 3). Selenium was rapidly excreted after ingestion of the selenium compounds: the peak concentrations (∼250–400 μg Se/L, normalized
concentrations) were recorded within 5–9 hours, and concentrations had returned to close to background levels within 48 hours,
by which time 25–40% of the ingested selenium, depending on the species ingested, had been accounted for in the urine. In
all experiments, the major metabolite was selenosugar 1, constituting either ∼80% of the total selenium excreted over the first 24 hours after ingestion of selenite or L-selenomethionine or ∼65% after ingestion of DL-selenomethionine. Selenite was not present at significant levels (<1 μg Se/L) in any of the samples; selenomethionine was
present in only trace amounts (∼1 μg/L, equivalent to less than 0.5% of the total Se) following ingestion of L-selenomethionine, but it constituted about 20% of the excreted selenium (first 24 hours) after ingestion of DL-selenomethionine, presumably because the D form was not efficiently metabolized. Trimethylselenonium ion, a commonly reported urine metabolite, could not be detected
(<1 μg/L) in the urine samples after ingestion of selenite or selenomethionine. Cytotoxicity studies on selenosugar 1 and its glucosamine isomer (selenosugar 2, methyl-2-acetamido-2-deoxy-1-seleno-β-D-glucosopyranoside) were performed with HepG2 cells derived from human hepatocarcinoma, and these showed that both compounds
had low toxicity (about 1000-fold less toxic than sodium selenite). The results support earlier studies showing that selenosugar
1 is the major urinary metabolite after increased selenium intake, and they suggest that previously accepted pathways for human
metabolism of selenium involving trimethylselenonium ion as the excretionary end product may need to be re-evaluated. |
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Keywords: | Selenium metabolism Selenosugar HPLC ICPMS Urine |
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