Effects of probucol on the composition and in vitro catabolism of LDL in type IIa hypercholesterolemia.

A possible mechanism of action of probucol on low density lipoprotein uptake was examined in 7 type IIa hypercholesterolemic subjects. Probucol administration effectively lowered plasma cholesterol. Both apo B-associated cholesterol and HDL cholesterol were decreased but a great inter-patient variability was noted. Plasma triglycerides were unchanged and phospholipids decreased. The composition of the isolated LDL was unaffected. The LDL displaceable activity of reference [125I]LDL measured by competition assays in control fibroblasts, was increased in 3 subjects, decreased in 1 subject and unchanged in the other 3. No correlation was found between the change in apo B-associated cholesterol and the change in the in vitro catabolism of LDL of treated patients. The results did not allow a simple mechanism of action to be ascribed to the drug, but questioned the origin of the hypercholesterolemia.