Metabolism of selenite in men with widely varying selenium status

Objective: This study was undertaken to investigate the metabolism of selen ite in men with life-long intakes of deficient, adequate and excess seleniu m. Methods: Stable isotopes of selenium were infused for five hours into Chine se men living in deficient, adequate or excessive selenium areas, and 24-ho ur urine and blood samples were collected daily for the next seven days. St able isotopic selenium excretion was determined in urine and in whole plasm a and plasma fractions. Results: Even though there was a positive correlation of selenium intake wi th the urinary excretion of this element, this relationship was not linear over the entire range (deficient, adequate, excessive) of selenium intake. When the urine excretion was normalized internally within each group, a sha rp increase in the slope of this relationship was found when long-term inta ke increased to adequate amounts, but the slope reached a plateau when the daily intake exceeded the adequate group. The plasma selenoprotein P fracti on was labeled initially, bur the incorporation in the glutathione peroxida se fraction subsequently increased by a small amount. A two-month dietary r estriction of selenium of the subjects from the excess area did not result in a reduction of urinary excretion of infused selenite. Conclusion: A complex relationship exists between long-term intake of selen ium and selenium status, and subjects living in the excess area are more sa turated with selenium than anticipated. More than two months of depletion a re required to affect urinary excretion of selenium.