Role of Glutathione in Reproductive Tract Secretions on Mouse Preimplantation Embryo Development1

We investigated the hypothesis that glutathione (GSH) in re-productive tract secretions (RTS) protects the preimplantation embryo from endogenous reactive oxygen species and is impor-tant for normal development during the embryo’s sensitive pe-riod when it is incapable of synthesizing GSH de novo. Mice were administered buthionine sulfoximine (BSO) to inhibit GSH synthesis and decrease GSH concentration in RTS. Embryos were then allowed to develop either in vivo or in vitro in the presence of RTS and the GSH concentration of the embryos was quantified by HPLC and embryonic development was recorded. GSH concentration in RTS did not differ over the phases of the estrous cycle, but there were significant decreases in GSH con-centration on Day 2 of gestation and due to BSO treatment. Embryos allowed to develop in vivo and in vitro in RTS with decreased GSH concentration did not exhibit decreased devel-opment or GSH concentration. Oocytes exposed to BSO during maturation in vivo experienced a significant decrease in GSH concentration and an increase in percent of degenerate embryos when compared with control. These data suggest that most of the GSH in RTS does not play a critical role in normal preim-plantation embryo development but that GSH stored in the oo-cyte during maturation has an important role in subsequent em-bryo development. Our studies do not exclude the possibility that GSH in RTS plays an important role in protection of the preimplantation embryo during exposure to some toxicants. early development, embryo, female reproductive tract, oviduct, toxicolog