THE IMPACT OF FEMALE SEX-HORMONES ON SECONDARY PREVENTION OF ATHEROSCLEROSIS IN OVARIECTOMIZED CHOLESTEROL-FED RABBITS

The present study investigated the effect of female sex hormones and d iet on atherosclerotic arteries in rabbits. The animals were initially ovariectomized and then fed an atherogenic diet for 12 weeks (n = 60) . They were thereafter randomized to 5 groups of which one immediately was killed. Three of the remaining groups received a moderate atherog enic diet plus oral 17 beta-estradiol, levonorgestrel or no hormones, whereas the last group was fed a diet without hormones or cholesterol. During the second phase of the study, the rabbits receiving the moder ate atherogenic diet and no hormones had the highest serum concentrati on of cholesterol (48.0 +/- 3.4 mmol/l), whereas those having the chol esterol free diet had the lowest value (26.4 +/- 3.6 mmol/l) with the two hormone groups in between (mean +/- S.E.M., P < 0.05). The estradi ol group had only approximately half of the aortic accumulation of cho lesterol (854 +/- 155, nmol/mg) found in the levonorgestrel (1676 +/- 362) and moderate atherogenic diet (1829 +/- 361) groups (mean +/- S.E .M., P < 0.05). The estradiol group and the rabbits fed diet without h ormones or cholesterol(1034 +/- 169) had a comparable degree of athero sclerosis. In conclusion, estradiol inhibits progression of atheroscle rosis significantly. This beneficial effect is only partly explained b y changes in serum lipids and lipoproteins.