Estrogen increases eNOS and NOx release in human coronary artery endothelium

Estrogen protects against the development of coronary heart disease in wome n. This study was designed to examine the direct effects of estrogen on nit ric oxide release and endothelial nitric oxide synthase (eNOS) expression i n cultured human coronary artery endothelial cells (HCAECs). NOx (nitrate, nitrite, and nitric oxide) was measured by the chemiluminescence method. Pr olonged treatment (48 h) of the cells with 17 beta-estradiol (E2P), but not 17 alpha-estradiol (E(2)alpha), resulted in a 2.3-fold increase in basal N Ox release in HCAECs and an enhanced adenosine triphosphate (ATP)- and calc ium ionophore A23187-indrrced NOx release. The effects of E(2)beta on endot helial NOx release were blocked by estrogen-receptor antagonist ICI 182,780 . E2P had no effect on basal and ATP-stimulated intracellular Ca2+ concentr ations in HCAECs. How ever, E(2)beta significantly increased eNOS protein l evels, as determined by Western analysis. We conclude that estrogen increas es NOx release in HCAECs, which is independent of cytosolic Ca2+ mobilizati on and is mediated by the upregulation of eNOS.