Studies of the metabolism of alpha-tocopherol stereoisomers in rats using [5-methyl-(14)C]SRR- and RRR-alpha-tocopherol.
We investigated the distribution and metabolism of SRR-alpha-tocopherol (SRR-alpha-Toc), synthetic alpha-Toc compared with RRR-alpha-Toc, in rats after a single oral administration of 2 mg (20 microCi) SRR- and RRR-alpha-[5-methyl-(14)C]Toc. In the liver, there was no difference in the recovery of radioactivity until 12 h after administration, and it reached a maximum of 4.4% of the dose after 12 h, but in other tissues, radioactivity derived from RRR-alpha-Toc was clearly higher than that derived from SRR-alpha-Toc after 12 h. For 96 h after administration, urinary excretions of SRR-alpha-Toc were 7.8% of the dose and significantly greater than that of RRR-alpha-Toc, which was 1.3% of the dose. On the other hand, total fecal excretions of SRR- and RRR-alpha-Toc were 87.6% and 83.0%, respectively. Therefore, radioactivity in the urine was assumed to have transferred out of the liver. Furthermore, the urine samples were hydrolyzed with 3 N methanolic HCl and analyzed by high performance liquid chromatography (HPLC) and liquid chromatography/mass spectrometry. The results showed that about 73% of the total radioactivity injected into HPLC was found to be 2,5,7, 8-tetramethyl-2-(2'-carboxyethyl)-6-hydroxy chroman (alpha-CEHC), as well as RRR-alpha-Toc. Thus, there is no difference between SRR-alpha-Toc and RRR-alpha-Toc in metabolic pathways, and it is suggested that SRR-alpha-Toc discriminated in the liver is rapidly metabolized by the liver and excreted as the conjugate of alpha-CEHC in the urine.
Kaneko
K
K
Institute of Environmental Science for Human Life, Ochanomizu University, Bunkyo-ku, Tokyo 112-8610, Japan.
Kiyose
C
C
Ueda
T
T
Ichikawa
H
H
Igarashi
O
O
D000818:Animals; D001345:Autoradiography; D002250:Carbon Radioisotopes; D002851:Chromatography, High Pressure Liquid; D008297:Male; D013058:Mass Spectrometry; D051381:Rats; D011916:Rats, Inbred F344; D013237:Stereoisomerism; D014810:Vitamin E / Q000031:analogs & derivatives / Q000737:chemistry / Q000378:metabolism* / Q000652:urine
D002250:Carbon Radioisotopes; D014810:Vitamin E