GLUTATHIONE IS PRESENT IN REPRODUCTIVE-TRACT SECRETIONS AND IMPROVES DEVELOPMENT OF MOUSE EMBRYOS AFTER CHEMICALLY-INDUCED GLUTATHIONE DEPLETION

We investigated the hypothesis that reduced glutathione (GSH) is prese nt in secretions of the female reproductive tract and that this extrac ellular GSH may protect preimprantation mouse embryos after intracellu lar GSH depletion. The cleavage-stage mouse embryo cannot synthesize G SH de novo and is unable to recover from glutathione depletion in vitr o. Analysis of GSH and total protein of oviduct flushings, quantified by HPLC and the Bradford method, respectively, revealed 51 nmol GSH pe r mg total protein. Embryos were treated with 60 mu M diethyl maleate (DEM) to deplete cellular GSH. When cultured with 1 mM GSH, these embr yos exhibited improved development compared to those cultured in contr ol medium (96% vs. 87% morula [p < 0.05], 78% vs. 75% blastocyst, 58% vs. 54% expanded blastocyst, 21% vs. 17% initiating hatching blastocys t). However, intracellular GSH content of embryos was not significantl y increased by the culture of DEM-treated embryos in medium containing GSH for 16, 40, or 64 h of incubation, suggesting that the embryo is not capable of taking up intact GSH. Furthermore, addition of buthioni ne sulfoximine (which inhibits synthesis of GSH) or acivicin (which in hibits breakdown of GSH at the membrane) to culture medium blocked the improvement in development. These data suggest that GSH in reproducti ve tract fluid may help protect preimplantation embryos from the adver se effects of toxicant-induced and endogenous depletion of embryonic G SH.