A possible role of progesterone receptor in mouse oocyte in vitro fertilization regulated by norethisterone and its reduced metabolite

BackgroundThe contraceptive effect of the progestogen norethisterone (NET) and its main metabolites 5α-NET and 3β,5α-NET has been demonstrated in several species, and most studies have focused on the effects of these compounds in the uterus. We previously reported that 5α-NET inhibits the progesterone (P4)-induced acrosome reaction in pig and mouse spermatozoa and induces severe morphological damage in two-cell fertilized mouse oocytes.Study DesignThe main goal of this study was to analyze the possible role of P4 receptor (PR) in the effects of NET and 5α-NET on the oocyte fertilization process. Different steroid treatments were used with or without cumulus-enclosed oocytes.ResultsIt was demonstrated that NET increases the percentage of fertilized oocytes in the same manner as P4 does, while 5α-NET reduces the percentage of fertilized oocytes. This effect was not reversed by P4 in the same concentrations.ConclusionA possible molecular mechanism for the effects of 5α-NET may be through a PR localized in the oocyte plasma membrane.