Metabolic pathway for selenium in the body: speciation by HPLC-ICP MS with enriched Se

Area of Science:

• Biochemistry
• Nutritional Science
• Toxicology

Background:

• Selenium (Se) is an essential trace nutrient with various inorganic and organic forms.
• Understanding the distinct metabolic fates of different selenium species is crucial for nutritional and toxicological assessments.

Purpose of the Study:

• To elucidate the metabolic pathways of inorganic selenium (selenite and selenate) in vivo.
• To identify the chemical species and distribution of absorbed selenium in rats.

Main Methods:

• Intravenous administration of enriched 82Se-selenite and 82Se-selenate to rats.
• Speciation analysis using gel filtration High-Performance Liquid Chromatography (HPLC) coupled with Inductively Coupled Plasma Mass Spectrometry (ICP-MS).
• Quantification of 82Se concentrations in organs and body fluids over time.

Main Results:

• Selenite rapidly entered red blood cells, was reduced to selenide, and transported to the liver bound to albumin.
• Selenate was either directly taken up by the liver or excreted in urine; it did not enter red blood cells.
• Two distinct selenium metabolites (A and B) were identified in the liver; metabolite A was methylated to metabolite B, a selenosugar, which is the major urinary metabolite.

Conclusions:

• Selenide serves as a common intermediate in selenium metabolism, regulating the balance between selenoprotein synthesis and excretion.
• Distinct metabolic pathways exist for selenite and selenate, influencing their bioavailability and distribution.
• The identification of selenosugar as a major metabolite highlights a key pathway for selenium excretion.