Half-lives of α-tocopherol in plasma have been reported as two to three days whereas the Elgin Study required > 2 y to deplete α-tocopherol. Therefore, gaps exist in our quantitative understanding of human RRR-α-tocopherol metabolism. Six men and 6 women age 27±6 (mean ± SD) ingested 1.81 nmol, 3.70 kBq of [5-14CH3]-RRR-α-tocopherol. The levels of 14C in blood plasma and washed red blood cells were monitored from 0-460 d while the levels of 14C in urine and feces were monitored from 0-21 d. A total of 23.24% of the dose was eliminated in feces over 21 d whereas only 4.26 % was eliminated via urine. The amount retained in the body from mass balance was 72.5±5.5%. The half-life of α-tocopherol varied in plasma and RBC according to the duration of study. The 14C levels in neither plasma nor RBC had returned to baseline by d 460, indicating that the t1/2 of [5-CH 3]-(2R, 4'R, 8'R)-α-tocopherol in human blood was longer than prior estimates. Also, a rapid, simple method for detecting 14C-α-tocopherol in lipoprotein fractions by AMS was developed. This single ultracentrifugation method accommodated plasma samples ranging from 2-25 uL by using 15% w/v CsBiEDTA density solution. Utilization of a 96 well plate SPE to desalt and extract 14C-α-tocopherol allowed the 14C-α-tocopherol within the lipoproteins to be quantified by AMS. The availability of this high throughput lipoprotein separation and detection method made the analysis of 14C-α-tocopherol in each lipoprotein fraction at multiple time points after dosing possible.
|Advisor:||Clifford, Andrew J.|
|Commitee:||Holstege, Dirk M., Novotny, Janet A.|
|School:||University of California, Davis|
|Department:||Agricultural and Environmental Chemistry|
|School Location:||United States -- California|
|Source:||DAI-B 73/01, Dissertation Abstracts International|
|Subjects:||Analytical chemistry, Nutrition|
|Keywords:||Accelerator mass spectrometry, Carbon isotopes, Intestinal absorption, Pharmacokinetics, Tocopherol, Vitamin E|
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