Improvement in the endothelium-dependent relaxation in hypercholesterolemic rabbits treated with vitamin E

The authors studied the time course of the vitamin E mediated improvement i n endothelium-dependent relaxation in hypercholesterolemic rabbits. A total of 40 male New Zealand white rabbits were randomly assigned to hypercholes terolemic (control) and vitamin E treated groups. The latter group was furt her divided in three subgroups in accordance with the duration of the vitam in E treatment (2, 4 or 6 days) at the end of the experiment. The dose of v itamin E utilized was 50 IU/day administered once a day by gavage. All the rabbits were fed a diet supplemented with cholesterol (0.5%) and coconut oi l (2%) for 4 weeks. At the end of this period, the animals were sacrificed and the aorta removed for determination of the cholesterol and malondialdeh yde (MDA) contents. The relaxation of the aortic strips in response to acet ylcholine was also studied. In addition, the cholesterol and MDA contents o f native and oxidized LDL were measured. At the end of the 4th week, the MD A level was significantly reduced in native and oxidized LDL in the rabbits treated with vitamin E for 2 days, while in aortic tissue a reduction was seen after 4 days of treatment. Endothelium-dependent relaxation improved s ignificantly after 6 days of vitamin E administration, and there was a redu ction in the total plasma and aortic cholesterol levels during this same pe riod. We conclude that vitamin E at a dose of 50 IU/day for 6 days improves the endothelium-dependent relaxation seen in hypercholesterolemic rabbits. This effect may be mediated through an antioxidant action on LDL particles and on the aortic arterial wall. (C) 1998 Elsevier Science Ireland Ltd. Al l rights reserved.