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 74SeO3(2-) 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 (WSe-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, WSe-EMP,7d decreased from 4.49 +/- 0.28 to 3.76 +/- 0.22 mg (p less than 0.05). The corresponding 24-h urinary selenium concentration dropped from 0.556 +/- 0.035 to 0.341 +/- 0.058 mumol/d (means +/- 1 SEM). Route of administration (iv vs po) had no apparent effect on WSe-EMP. In subjects of similar selenium status, the WSe-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.