Monitoring vitamin E pools in sheep tissue and plasma after intravenous dosing of radiotocopherol

Abstract

The fate of radiotocopherol was studied in plasma and tissues of sheep at various intervals after injection of single intravenous doses of 3 H-labelled D-α-tocopherol. Plasma samples were taken at regular intervals after dosing and selected tissues were taken from all sheep after slaughter and assayed for radioactivity and D-α-tocopherol. Sheep were killed in groups of five at 24, 72, 96, 272 and 432 h post-dosing. Plasma profiles were characterized as a sum of three exponential terms. A principal component analysis of tissue concentrations was carried out to identify tissues with parallel profiles of log (disintegrations/min per μg) over time. Five groups of tissues with distinct uptake and elimination processes were identified. The D-α-tocopherol in the liver and heart appeared to be consistent with the post-distributive kinetics of a highly perfused shallow compartment, while lung kinetics appeared to reflect a non-linear kinetic process. The third group, which included the spleen, neck brachiocephalicus muscle and pancreas, had depletion rates parallel to those of plasma for 24–272 h, but slower decreases than plasma over 272–432 h. Hip gluteus muscle and kidney comprised a fourth group, with depletion parallel to plasma rates for 24–96 h but progressively slower than plasma decreases over 96–272 h. Adrenal kinetics resembled the fourth group, but had a more rapid decrease in specific activities over 24–72 h.