The effect of percutaneous oestradiol on atheroma formation in ovariectomized cholesterol-fed rabbits

Objective: The aim of this study was to examine the effect of percutaneous oestradiol on the lipid profile and on atheroma formation using an animal m odel. Methods: The study was of 12 weeks duration. Fifty sexually mature fe male New Zealand White rabbits were divided into five groups of equal size. Two groups acted as controls and received normal rabbit chow. Rabbits in o ne of these groups were ovariectomized. The remaining three groups were ova riectomized but received 1% cholesterol enriched rabbit chow. One of these cholesterol-fed groups received 0.3 mg/kg percutaneous oestradiol daily whi lst another received 0.1 mg/kg oral oestradiol daily. Measurements of conce ntrations of total cholesterol (TC), high density lipoprotein cholesterol ( HDL-C) and triglycerides (TC) were made at the beginning and end of the stu dy. Aortic atheroma formation was measured using computerized image analysi s of uptake of Sudan III staining. Results: After 12 weeks there were signi ficant increases in the mean concentrations of TC in the three cholesterol- fed groups compared with controls (P < 0.001). Changes in HDL-C and TG conc entrations were less consistent. The mean area of aortic atheroma formation was significantly less in both the percutaneous oestradiol group (4.9%) an d the oral oestradiol group (8.6%) compared with the non-oestrogen-treated cholesterol-fed group (19.5%) (P < 0.001, < 0.01 respectively). Conclusion: These results suggest that percutaneous oestradiol has a direct protective effect on atheroma formation independent of serum concentrations of total cholesterol. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.