Effect of probucol on plasma clearance and organ uptake of chylomicrons and VLDLs in normal and diabetic rats.

Probucol was given to rats made diabetic by streptozotocin. Compared with diabetic rats not receiving probucol or with nondiabetic rats, probucol lowered the plasma concentrations of triglycerides, phospholipids, cholesterol, and apolipoprotein B. The concentrations of serum chylomicrons and very low density lipoprotein (VLDL) were also reduced. In control and diabetic rats, probucol enhanced the clearance of endogenously radiolabeled VLDL from the plasma. Clearances from the plasma of rat lymph chylomicrons or chylomicron-like lipid emulsions were slow in diabetic rats. Probucol normalized chylomicron clearance in diabetic rats primarily by restoring hepatic uptake of remnants, which was decreased in diabetes. In diabetic rats, uptake of chylomicron remnants was increased in a number of extrahepatic tissues, including the heart and kidney. Probucol significantly decreased uptake in some extrahepatic tissues. Increased plasma clearance of VLDL and chylomicrons was associated with an increase in the apolipoprotein CII/CIII and apolipoprotein E/C ratios. Orally administered probucol was specifically incorporated into lymph chylomicrons, and clearance of probucol from the plasma exactly paralleled the clearance of chylomicron remnants, as traced with radiolabeled cholesteryl esters. Chylomicron-like emulsions incorporating probucol were exclusively cleared from the plasma by the liver in normal rats. We conclude that in streptozotocin diabetic rats, probucol is an effective hypolipidemic agent because it promotes the clearance of the triglyceride-rich lipoproteins.