['Estrogen reverses acetylcholine-induced coronary vasoconstriction via the possible facilitation of endothelium-derived NO. Estrogen also affects endothelium-derived constrictor factors. We therefore investigated the effects of 17beta-estradiol on coronary vasomotor responses to substance P (SP), and coronary sinus endothelin-1 and NO metabolite levels in postmenopausal women with coronary heart disease.', 'We studied 20 women; 14 received estrogen (mean age 65+/-2 years) and 6 served as ethanol control subjects (age 63+/-3 years). Intracoronary infusions of papaverine (8 mg) and SP were administered before and 20 minutes after 50 pg/min 17beta-estradiol or 0.2 microL/min control. Coronary blood flow was calculated from the diameter, as measured with quantitative coronary angiography, and flow velocity, as measured with intracoronary Doppler. Coronary sinus plasma endothelin-1 and nitrite/nitrate (NO(2)/NO(3)) were measured at baseline, at peak velocity response to each infusion, and every 5 minutes during the estradiol infusion. Endothelin-1 levels were decreased after 20 minutes of estradiol (1.12+/-0.18 versus 0.86+/-0.17 pmol/L baseline2 versus estradiol, P:=0.05). Endothelin-1 levels to SP decreased after 17beta-estradiol (1.29+/-0. 18 versus 1.04+/-0.15 and 1.3+/-0.16 versus 0.99+/-0.17 pmol/L for before versus after estradiol, 10 and 25 pmol/min SP; both P:<0.05). NO(2)/NO(3) levels did not change. There was no change in vasomotor responses to estradiol alone or to papaverine or SP before versus after estradiol.'] Does 17beta-estradiol decrease endothelin-1 levels in the coronary circulation of postmenopausal women with coronary artery disease?