Urocortin 1 (Ucn1) is a 40-amino-acid peptide that has vasodilatory activity and displays immunomodulatory and antioxidant properties. Maternal and cord plasma Ucn1 levels are increased in preeclampsia and preterm labor, but the mechanisms of such increase are poorly known. Thus, we investigated Ucn1 localization in human umbilical cord and assessed some potential stimuli to Ucn1 release by human umbilical vein endothelial cells (HUVEC). Human umbilical cords were obtained at uncomplicated term pregnancy (n=11). Ucn1 localization was assessed by immunohistochemistry and quantified. HUVEC were grown in vitro to confluence, then incubated with serial concentrations of interleukin (IL)-8, interferon (INF)-γ, lipopolysaccharide (LPS), endothelin (ET)-1, prostaglandin (PG)F-2α, estradiol, progesterone and dexamethasone and Ucn1 concentrations were measured in the supernatants. Ucn1 was immunolocalized with similar intensity in umbilical cord arteries, vein and Wharton's jelly. Ucn1 mRNA was detected in all HUVEC cultures and Ucn1 peptide was detectable in culture medium from untreated cells at different time points. Incubation with IFN-γ increased Ucn1 secretion in a dose-dependent manner. Treatments with IL-8, LPS, ET-1 and dexamethasone were able to increase three to fourfold Ucn1 release from cultured endothelial cells. In conclusion, umbilical vessels express Ucn1 and may be a contributive source of Ucn1 release into fetal-placental circulation. IL-8, IFN-γ, LPS, ET-1 and dexamethasone promote Ucn1 secretion from cultured HUVEC.