Biokinetics and biliary excretion of radiotocopherol administered orally to sheep.

: Four adult sheep were given .4 microCi/kg of BW of D-alpha[5-Me-3H]tocopherol orally. Plasma alpha-tocopherol specific activities were measured serially during a 72-h period, after which the sheep were killed. The disposition kinetics were best described by the use of a two-compartment model. The radiotocopherol had a slow distribution phase followed by a relatively slow elimination phase. During the 72-h period of serial monitoring the peak plasma specific activities were observed between 32 to 48 h. At slaughter (72 h after dosing) tissue radioactivity distribution indicated a high rate of accumulation in some glandular organs such as the liver and adrenals. Identification of radioactive components excreted in bile, using HPLC or thin-layer chromatography, showed that unchanged radiotocopherol was present only at very low concentrations (less than 3% of the total recovered radioactivity).