THE SELENITE-EXCHANGEABLE METABOLIC POOL IN HUMANS - A NEW CONCEPT FOR THE ASSESSMENT OF SELENIUM STATUS

An in vivo isotope-dilution approach is considered for assessment of selenium status in human subjects. The approach depends upon the dilution of a single dose of the stable isotope 74SeO32- in the selenite-exchangeable metabolic pool. Data from six metabolic protocols, conducted with healthy North American males, are presented in order to analyze characteristics of this pool. Pool size (W(Se-EMP)) correlated positively with daily selenium intake in subjects consuming diets of known and variable selenium content. When subjects were given a selenium-adequate or -restricted diet for 30 d, W(Se-EMP,7d) decreased from 4.49 ± 0.28 to 3.76 ± 0.22 mg (p < 0.05). The corresponding 24-h urinary selenium concentration dropped from 0.556 ± 0.035 to 0.341 ± 0.058 μmol/d (x̄ ± 1 SEM). Route of administration (iv vs po) had no apparent effect on W(Se-EMP). In subjects of similar selenium status, the W(Se-EMP) was reproducible within the expected uncertainties of the method. This approach may be suitable for assessment of selenium status for a wide range of chronic intakes.