Quantitation of rat liver vitamin E metabolites by LC-MS during high-dose vitamin E administration.
To evaluate vitamin E metabolism, a method was developed to quantitate liver alpha- and gamma-tocopherol metabolites, alpha-carboxyethyl hydroxychroman [alpha-CEHC; 2,5,7,8-tetramethyl-2-(2'-carboxyethyl)-6-hydroxychroman] and gamma-CEHC [2,7,8-trimethyl-2-(2'-carboxyethyl)-6-hydroxychroman], respectively. Vitamin E supraenriched livers were obtained from rats that were injected with vitamin E daily for 18 days. Liver samples (approximately 50 mg) were homogenized, homogenate CEHC-conjugates were hydrolyzed, CEHCs were extracted with ethyl ether, and then CEHCs were quantitated using liquid chromatography-mass spectrometry (LC-MS). Precision, based on intersample variability, ranged from 1% to 3%. Recovery of alpha- and gamma-CEHCs added to liver homogenates ranged from 77% to 87%. Detection limits of alpha- and gamma-CEHC were 20 fmol, with a linear detector response from 0.025 to 20 pmol injected. Corresponding with an increase in liver alpha-tocopherol, the MS peak for liver alpha-CEHC (mass-to-charge ratio 277.8) increased 80-fold (0.18 +/- 0.01 to 15 +/- 2 nmol/g). Liver alpha-CEHC concentrations were correlated with serum alpha-CEHC, liver alpha-tocopherol, and serum alpha-tocopherol (P < 0.001 for each comparison). alpha-CEHC represented 0.5-1% of the liver alpha-tocopherol concentration. Thus, LC-MS can be successfully used to quantitate alpha- and gamma-CEHC in liver samples. These data suggest that in times of excess liver alpha-tocopherol, increased metabolism of alpha-tocopherol to alpha-CEHC occurs.
Leonard
Scott W
SW
Linus Pauling Institute, Oregon State University, Corvallis, OR, USA.
Gumpricht
Eric
E
Devereaux
Michael W
MW
Sokol
Ronald J
RJ
Traber
Maret G
MG
D000818:Animals; D002853:Chromatography, Liquid / Q000379:methods*; D007700:Kinetics; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D015203:Reproducibility of Results; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D024505:Tocopherols / Q000097:blood / Q000378:metabolism; D014810:Vitamin E / Q000378:metabolism*
D014810:Vitamin E; D024505:Tocopherols