Mechanisms of absorption, transport and tissue uptake of RRR-alpha-tocopherol and d-gamma-tocopherol in the white rat.
The metabolism of alpha- and gamma-tocopherol was studied in three groups of rats that were fed a modified AIN-76 diet containing normal (NE, 0.2 g alpha-tocopherol/kg), high (HE, 1.0 g alpha-tocopherol/kg) or low (LE, less than 0.02 alpha-tocopherol/kg) vitamin E for 3 mo. After 1, 2 and 3 d of an oral dose of 20 mg of alpha-tocopherol, gamma-tocopherol or both, the levels of the two vitamers were measured in plasma and tissues and in some cases in isolated microsomal and mitochondrial fractions from liver. Twenty-four hours after an oral dose of 20 mg gamma-tocopherol the levels of alpha-tocopherol in plasma and tissues remained constant and higher levels of gamma-tocopherol were found in tissues in which low alpha-tocopherol levels could be found such as in the LE group. In spite of this, it was enabled to remain there, after 2 and 3 d gamma-tocopherol had decreased levels in all tissues. When given in combination with alpha-tocopherol, the levels of gamma-tocopherol were lower than when gamma-tocopherol was given alone. Microsomes and mitochondria from livers of LE group bound five and nine times more alpha-tocopherol than gamma-tocopherol in rats dosed with equal amount of alpha- or gamma-tocopherol, respectively. These data indicate that the mechanisms that regulate the metabolism of vitamin E are highly specific for alpha-tocopherol. Moreover, the relative amount of alpha-tocopherol determined the levels of gamma-tocopherol in tissues. However, the retention of gamma-tocopherol in tissues did not depend on the presence of alpha-tocopherol.(ABSTRACT TRUNCATED AT 250 WORDS)
Behrens
W A
WA
Bureau of Nutritional Sciences, Health and Welfare Canada, Ottawa, Ontario.
Madere
R
R
D000042:Absorption; D000818:Animals; D001692:Biological Transport; D004032:Diet; D004912:Erythrocytes / Q000378:metabolism; D007700:Kinetics; D008099:Liver / Q000378:metabolism; D008297:Male; D008862:Microsomes, Liver / Q000378:metabolism; D008930:Mitochondria, Liver / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D013154:Spleen / Q000378:metabolism; D014018:Tissue Distribution; D014810:Vitamin E / Q000008:administration & dosage / Q000493:pharmacokinetics*
D014810:Vitamin E