Vitamin E binds to specific binding sites and enhances prostacyclin production by cultured aortic endothelial cells.

We evaluated the effect of d-alpha-tocopherol (vitamin E) on the production of prostacyclin (PGI2) by cultured bovine aortic endothelial cells. Vitamin E at physiological doses significantly enhanced the production of PGI2 by aortic endothelial cells when added to the culture simultaneously with histamine, the Ca2+ ionophore A23187 (A23187), plasma-derived serum (PDS), or arachidonic acid. This effect was found to occur in a time- and dose-dependent manner, and the maximal enhancement was produced by 9.28 microM of vitamin E for 1 h incubations. Significantly lower amounts of lipid peroxides were measured in endothelial cells stimulated by 10% PDS with 9.28 microM of vitamin E than in those stimulated without vitamin E for over 24 h, although the stimulation during the initial 1 to 12 h period did not have a significant effect on lipid peroxide formation in cultured aortic endothelial cells. We also demonstrated that bovine aortic endothelial cells have specific binding sites for [3H]vitamin E that exhibited time- and temperature-dependent saturability. At 4 degrees C, the nonspecific binding was 8-12% of the total binding, and the specific binding reached equilibrium by 2 h. Specific binding increased with the concentration of [3H]vitamin E and became saturated at concentrations between 1.5 microM and 2.0 microM per 2.0 x 10(5) cells. Raising the unlabeled vitamin E concentration from 97.7 nM to 1,000 microM reduced the specific binding of 2.0 microM [3H]vitamin E.(ABSTRACT TRUNCATED AT 250 WORDS)