A human model of selenium that integrates metabolism from selenite and selenomethionine.

Selenium (Se) metabolism is affected by its chemical form in foods and by its incorporatior (specific vs nonspecific) into multiple proteins. Moor:lino Se kinetics may clarify the impact of form or metabolism. Although the kinetics of Se forms have been compared in different participants, or the same participants at different times, direct comparisons of their respective metabolism in :he same participants have rot been made. The aim of this study was to simultaneous y compare kinetics of absorbed Se from inorganic selerite (Sol) and organic selenomethionine (SeMet) in healthy participants (n= 31). After oral administration of staple solopic trace's of each form, urine and feces were collected for 12 d and blood was sampled over 4 mo. Tracer enrichment was determined by isotope-dilutior-GC-MS. Using WinSAAM, a compartmental model was fited to the data Within 30 mn of ingest on, Se from both forms entered a common poo., and metabolism was similar for severa days before diverging. Slow y turning-over pools were required in tissues and plasma for Se derived from SeMet to account for its 3-times-higher incorporation into RBC compared with Se from Sal; these presumably represent nonspecific incorporation of SeMet into proteins. Pool sizes and transport rates were determined and comparea by form and gender. The final model consisted of 11 plasma pools, 2 pools and a delay in RBC, and extravascular pools for recycling of Se back into plasma. This model will be used to evaluate charges in Se metabolism following long-term (2 y) Se supplementation. J. Nutr. 141: 708-717. 2011.