Estradiol-17beta (E(2)beta) and its metabolites, which are sequentially synthesized by cytochrome P450s and catechol-O-methyltransferase to form 2 and 4-hydroxyestradiol (OHE(2)) and 2- and 4-methoxestradiol (ME(2)), are elevated during pregnancy. We investigated whether cytochrome P450s and catechol-O-methyltransferase are expressed in uterine artery endothelial cells (UAECs) and whether E(2)beta and its metabolites modulate cell proliferation via ER-alpha and/or ER-beta and play roles in physiological uterine angiogenesis during pregnancy. Cultured ovine UAECs from pregnant and nonpregnant ewes were treated with 0.1 to 100.0 nmol/L of E(2)beta, 2-OHE(2), 4-OHE(2), 2-ME(2), and 4-ME(2). ER-alpha or ER-beta specificity was tested using ICI 182 780, ER-alpha-specific 1,3-bis(4-hydroxyphenyl)-4-methyl-5-[4-(2-piperidinyleth oxy)phenol]-1H-pyrazole dihydrochloride, ER-beta-specific 4-[2-phenyl-5,7-bis(trifluoromethyl)pyrazolo [1,5-a]pyrim idin-3-yl]phenol antagonists and their respective agonists ER-alpha-specific 4,4',4"-(4-propyl-[1H]-pyrazole-1,3,5-triyl)trisphenol and ER-beta-specific 2,3-bis(4-Hydroxyphenyl)-propionitrile. Angiogenesis was evaluated using 5-bromodeoxyuridine proliferation assay. Using confocal microscopy and Western analyses to determine enzyme location and levels, we observed CYP1A1, CYP1A2, CYP1B1, CYP3A4, and catechol-O-methyltransferase expression in UAECs; however, expressions were similar between nonpregnant UAECs and pregnant UAECs. E(2)beta, 2-OHE(2), 4-OHE(2), and 4-ME(2) treatments concentration-dependently stimulated proliferation in pregnant UAECs but not in nonpregnant UAECs; 2-ME(2) did not stimulate proliferation in either cell type. Proliferative responses of pregnant UAECs to E(2)beta were solely mediated by ER-beta, whereas responses to E(2)beta metabolites were neither ER-alpha nor ER-beta mediated. We demonstrate an important vascular role for E(2)beta, its cytochrome P450- and catechol-O-methyltransferase-derived metabolites, and ER-beta in uterine angiogenesis regulation during pregnancy that may be dysfunctional in preeclampsia and other cardiovascular disorders.