Variable expression of the estrogen receptor in normal and atherosclerotic coronary arteries of premenopausal women.

Abstract

BACKGROUND: The relative absence of coronary atherosclerosis in premenopausal women has been established. Estrogen is presumed to play a role in the protection of coronary arteries from atherosclerosis, and part of this protective effect appears to be mediated by amelioration of serum lipid profiles. However, all of the atheroprotective effect of estrogen is not explained by alteration of serum lipids. In this study, we attempt to identify evidence of estrogen receptors in coronary artery specimens of female patients and in human vascular smooth muscle cells. METHODS AND RESULTS: Postmortem coronary artery specimens were obtained from premenopausal (n = 18) and postmenopausal (n = 22) women who died with significant coronary artery disease (n = 19) and from noncardiac causes with normal coronary arteries (n = 21). Sections were examined for evidence of estrogen receptor expression using a monoclonal antibody stain. Radioligand binding assays for estrogen receptors were performed on human vascular smooth muscle cells in culture, and gel retardation assays were performed to confirm the presence of functional estrogen receptors. Estrogen receptor expression was identified by immunostaining in a total of 21 coronary arteries, with the majority of normal arteries (15 positive of 21 total, P = .0117) demonstrating evidence of estrogen receptor expression. Conversely, a minority (6 of 19, P = NS) of atherosclerotic arteries were positive for estrogen receptor expression. Furthermore, the relation between estrogen receptor expression and absence of coronary atherosclerosis was most evident in premenopausal subjects, with 10 of 12 normal arteries in this group demonstrating evidence of estrogen receptors, whereas only 1 of 6 atherosclerotic coronary arteries was positive (P = .0062). Radioligand binding assays confirmed the presence of estrogen receptors at significant concentrations in intact human vascular smooth muscle cells. Gel retardation assays also documented the presence of functional estrogen receptors in extracts from human vascular smooth muscle cells. CONCLUSIONS: This investigation provides evidence of estrogen receptors in smooth muscle cells from human coronary arteries. The demonstrated relation between the presence of the receptors and the absence of atherosclerosis in premenopausal women suggests that these receptors may play a functional role in coronary atheroprotection.