Objective:To determine the role of endothelin(EDN) signaling in the estradiol(E2) nongenomic and genomic mechanism that regulates egg transport in the oviduct.Methods:The effect of the selective agonists ofETA(BQ610) orETB(BQ788) on theE2-induced egg transport acceleration in unmated and mated rats was compared.Then, the level and distribution ofETA orETB in the oviduct of unmated and mated rats followingE2 treatment was analyzed.Finally, the effect of E2 on the oviductal release ofEDN1 in unmated and mated rats was determined.Results:The intraoviductalE2 nongenomic pathway required participation ofETA andETB while theE2 genomic pathway required onlyETA.Furthermore, expression ofETA andETB was present in the oviduct although their levels were similar between unmated and mated rats and followingE2 treatment. On other hand, bothEDN receptors were differentially localized in the oviductal cells whereETA was mainly localized in the apical zone of epithelial cells and in the stroma and muscle whileETB was localized exclusively in the apical zone of the epithelium.However, mating andE2 treatment did not affect the localization of these receptors in the oviductal cells.Conclusions:These results indicate that mating influences the role ofEDN signaling in the effect ofE2 on egg transport in the rat oviduct.This effect of mating onEDN signaling is not explained by a change in the expression or localization of their receptors along the oviduct.These findings provides the first evidence of an association between mating andEDN in order to modulate a physiological process regulated byE2 in the mammalian oviduct.