Excretion of trimethylselenonium ion in human urine

A method to permit isolation and measurement of trimethylselenonium ion TMSe, (CH3)3Se+] from 1 liter of human urine was developed. The method was based on precipitation of TMSe with ammonium reineckate, preseparation with anion-exchange resin, and final thermal decomposition and collection of the product in HNO3. It was tested for recovery and separation from other selenium moieties present in urine using both in vivo-labeled rat urine and human urine spiked with unlabeled TMSe. Recoveries from the former were in the range 76.8-87.0% (mean +/- SD: 81.8 +/- 3.7%, n = 5), while for the latter they were in the range 72.0-93.0% (mean +/- SD for three occasions (%): 80.9 +/- 5.5, 81.4 +/- 7.8, and 78.9 +/- 1.0). The reliability of the method was tested against an HPLC procedure using in vivo-labeled rat's urine. The mean (+/- SD) percentage of urine radioactivity appearing as TMSe was 36.0 +/- 5.7% for the present and 36.2 +/- 6.6% for the HPLC method. The mean of deviations, as percentage of the HPLC method, was -0.03 +/- 8.8%. The linear regression equation for the two methods was y = -0.805 + 1.029x (r2 = 0.81). Excretion of TMSe was measured in urine samples from several persons (range: 0.18-0.37 micrograms Se/liter; mean +/- SD: 0.26 +/- 0.07, n = 9). One subject consumed three separate doses of unlabeled selenite on alternate days (Day 1, 197 micrograms Se; Day 3, 395; and Day 5, 592). For the first 24 h of each period, TMSe excretions (micrograms Se/24 h) were 0.24, 0.53, and 0.97, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)