The mechanism(s) of uptake of vitamin E (alpha-tocopherol) by tissues is poorly understood. It has, however, been suggested from studies in vitro that the apolipoprotein B/E (apo B/E) receptor pathway for low-density lipoprotein (LDL) may be involved. To investigate the role of the apo B/E receptor pathway in vivo, we have studied the transport and uptake of alpha-tocopherol by tissues in Watanabe Heritable Hyperlipidaemic (WHHL) rabbits, which lack functional LDL (apo B/E) receptors, and controls. [3H]alpha-Tocopherol incorporated within LDL labelled with [14C]sucrose was used in these studies, as this enabled the uptake of both alpha-tocopherol and LDL to be studied independently. The principal findings were as follows. (1) Concentrations of the circulating lipids (including alpha-tocopherol) and LDL were increased and the plasma fractional disappearance rates of alpha-tocopherol and LDL decreased in the WHHL rabbits. (2) The WHHL rabbits clear more LDL and alpha-tocopherol from the circulation than controls do, because of their increased pool sizes of alpha-tocopherol and LDL. (3) The lipoprotein composition of the WHHL rabbits differed from that of the controls, and there was exchange of alpha-tocopherol between the lipoprotein fractions in vivo and in vitro. (4) High-affinity apo B/E receptors were not essential for the uptake of alpha-tocopherol by tissues. (5) Evidence from the plasma-clearance and tissue data suggest that alpha-tocopherol can be taken up by tissues in association with, and also independent of, LDL. We conclude that there are several different mechanisms for the uptake of alpha-tocopherol by tissues, which include receptor-dependent and receptor-independent pathways, independent transport and co-transport of alpha-tocopherol and LDL, and uptake from a number of different lipoproteins.
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October 1992
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Research Article|
October 01 1992
Plasma clearance and net uptake of α-tocopherol and low-density lipoprotein by tissues in WHHL and control rabbits
W Cohn;
W Cohn
*Department of Vitamin Research, F. Hoffmann-La Roche Ltd., CH 4002 Basle, Switzerland.
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M A Goss-Sampson;
M A Goss-Sampson
†Institute of Child Health, London WC1N 1EH, U.K.
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H Grun;
H Grun
*Department of Vitamin Research, F. Hoffmann-La Roche Ltd., CH 4002 Basle, Switzerland.
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D P R Muller
D P R Muller
†Institute of Child Health, London WC1N 1EH, U.K.
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Publisher: Portland Press Ltd
Online ISSN: 1470-8728
Print ISSN: 0264-6021
© 1992 The Biochemical Society, London
1992
Biochem J (1992) 287 (1): 247–254.
Citation
W Cohn, M A Goss-Sampson, H Grun, D P R Muller; Plasma clearance and net uptake of α-tocopherol and low-density lipoprotein by tissues in WHHL and control rabbits. Biochem J 1 October 1992; 287 (1): 247–254. doi: https://doi.org/10.1042/bj2870247
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