Effect of probucol on serum lipoprotein levels in normal and dyslipoproteinemic mice.

The effect of probucol was studied on serum lipoprotein levels in normal and cholesterol-fed, hypercholesterolemic mice. In normal mice, probucol caused a significant reduction in LDL + VLDL cholesterol at daily doses above 25-50 mg/kg and also in HDL cholesterol at higher doses. In cholesterol-fed mice, probucol treatment decreased LDL + VLDL cholesterol at daily doses exceeding 200 mg/kg and also HDL cholesterol at a daily dose of 800 mg/kg. The ratio of LDL + VLDL cholesterol to HDL cholesterol was significantly reduced by treatment at 25-100 mg/kg in normal mice and at 200 mg/kg in hypercholesterolemic mice. The ratio was not reduced at doses above these ranges. These dose-effect relationships were not modified by duration of probucol treatment. These findings suggest that there is an optimum dosage of probucol to lower LDL + VLDL cholesterol and the atherogenic index, and that the actual optimum dosage for the beneficial effect depends on blood lipid levels or types of hyperlipidemia. This may be important in the clinical application of this drug, because a negative correlation has been demonstrated between HDL cholesterol levels and ischemic heart disease. Clofibrate treatment did not affect serum lipid levels significantly in either normal or cholesterol-fed mice. Probucol was again effective in lowering LDL cholesterol values in cholesterol-fed mice which had previously been treated with clofibrate for 2 weeks without any beneficial effect. In an additional experiment, it was found that the probucol-induced reduction in cholesterol returned to the pre-treatment levels gradually over several days, depending on the dose and without rebound elevation after withdrawal of the drug.