Synthetic estrogen 17 alpha-ethinyl estradiol induces pattern of uterine gene expression similar to endogenous estrogen 17 beta-estradiol

17 alpha-Ethinyl estradiol is one of most widely prescribed estrogens. We c ompared the effects of this synthetic estrogen to those of the endogenous o varian hormone 17 beta-estradiol on the expression of four estrogen-inducib le genes in the rat uterus. The genes examined include c-fas, c-jun, vascul ar endothelial growth factor, and creatine kinase B, which ave all known to be primary responses to estrogen administration. Both estrogens induced th e four target genes with similar time courses and produced the same pattern of cell-specific expression of c-fas and vascular endothelial growth facto r in the uterine epithelium and stroma, respectively. Dose-response studies established that the potency and efficacy of both estrogens in the uterus were the same for all four hormone-regulated genes. These studies suggest t hat 17 alpha-ethinyl and 17 beta-estradiol produce similar if not identical patterns of gene expression in the uterus.