Elevation of serum HDL and HDL cholesterol in cholesterol-fed male rabbits treated with estrogen

The effect of cholesterol feeding and estrogen administration on serum lipoproteins and lipoprotein lipid composition was investigated in male rabbits. The lipoprotein fractions were separated by preparative ultracentrifugation and the purity of each fraction was determined by polyacrylamide disc gel electrophoresis. The amount of cholesterol, cholesterol ester, triglycerides and phospholipids was determined in each of the lipoprotein fractions. It was found that treatment of the cholesterol-fed animals with estrogen resulted in an increase of their serum HDL, HDL cholesterol, HDL phospholipids and HDL triglycerides. This increase was accompanied by a decrease in serum VLDL, VLDL cholesterol and VLDL phospholipids. Since increased HDL and HDL cholesterol have been known to be associated with lower coronary heart disease, the increased serum HDL and HDL cholesterol resulting from estrogen treatment might account for the reported lower incidence of coronary heart disease in young women than in young men and the protective effect of estrogen against diet-induced and spontaneous atherosclerosis in animals.