Abstract
We investigated the in vitro effects of probucol on the oxidation of isolated low density lipoprotein (LDL) and of plasma by cupric ions. We also studied changes in the concentrations of lipid peroxides and antioxidants in circulating blood following the oral administration of probucol.
(1) LDLs were dose-dependently oxidized in vitro by cupric ions. The oxidation of LDL by cupric ions was markedly enhanced in the presence of monocytes. Probucol markedly inhibited the oxidation of LDL. The antioxidant effects of probucol were more marked in the presence of cupric ions. On the other hand, plasma was only very slightly, if at all, oxidized by cupric ions in vitro, and the antioxidant effects of probucol were not clear. It was suggested that the antioxidants in plasma (particularly, vitamin C) and/or plasma protein protected plasma lipids from oxidation by cupric ions.
(2) After 500mg probucol were administered daily for two weeks, the thiobarbituric acid reactive substances of plasma decreased significantly, although the hydroperoxide of the plasma lipids remained unchanged.
(3) An increase in the plasma ubiquinol-10/ubiquinone-10 ratio was observed after the oral administration of probucol, suggesting some protective effects of probucol on ubiquinol-10 which is regarded as a natural antioxidant in vitro.
