Ovariectomized Cholesterol-Fed Rabbits

Cardiovascular disease is a major killer in postmenopausal women in the industrialized societies. To investigate the effect of progestogen and 17p-estradiol replacement therapy on atherogenesis, we studied 60 cholesterol-fed ovariectomized rabbits for 13 weeks. They were randomly assigned to four groups of 15 rabbits each and received oral treatment with norethisterone acetate, levonorgestrel, 17f3-estradiol, or placebo. The active treatment groups achieved serum hormone concentrations, which produced physiological effects on the uterus. No significant differences in serum total cholesterol or ultracentrifuged lipoproteins (very low density, intermediate density, low density, or high density lipoproteins) were found between the four groups during the experimental period. There were no significant differences between the progestogen and placebo groups in the aortic accumulation of cholesterol. The estradiol group had only accumulated about half the aortic cholesterol as compared with the placebo group and the progestogen