Abstract
Recent reports suggest that calcium channel blockers may be effective in preventing atherosclerosis in cholesterol-fed animals. But the antiatherogenic mechanism have not been well understood until recently. Therefore, we examined the effects of diltiazem and verapamil on metabolism of modified LDL in macrophages. Cultured mouse peritoneal macrophages accumulate large quantities of cholesteryl ester when incubated with acetylated low density lipoprotein (acetyl-LDL). To determine the effect of diltiazem or verapamil on the change in intracellular cholesterol reesterification, we incubated mouse peritoneal macrophages with acetyl-LDL (50μg protein/ml), 0.1 mM [14C]oleate albumin complex and Ca2+ antagonist (diltiazem or verapamil (10-6, 10-5 and 10-4M)) for 4 hours. After macrophages were harvested, cellular lipids were isolated using the Folch method. Intracellular cholesteryl [14C]oleate was isolated by thin layer chromatography. The composition of fatty acyl components of the cholesteryl esters was determined by high performance liquid chromatography.
Diltiazem 10-4M and verapamil 10-5M significantly decreased cholesterol reesterification, regardless of marked accumulation of cholesteryl ester in macrophage. The composition of fatty acyl components of the accumulated cholesteryl esters indicated a reduction in cholesteryl oleate and an increase in cholesteryl linoleate. These results suggest that diltiazem 10-4M and verapamil 10-5M could suppress degradation of acetyl-LDL in mouse peritoneal macrophages.
