Differential glutathione depletion by L-buthionine-S,R-sulfoximine in rat embryo versus visceral yolk sac in vivo and in vitro.

L-Buthionine-S,R-sulfoximine (L-BSO), a selective inhibitor of glutathione synthesis, exhibited the capacity to deplete embryonic and visceral yolk sac glutathione (GSH) after administration in vivo and also after addition of L-BSO to a whole embryo culture system. Administration of L-BSO to pregnant dams at 2.5 or 18 hr prior to the explantation of day 10 conceptuses resulted in greater than 55% GSH depletion relative to control values in both the yolk sac and the embryo proper. The levels of GSH returned to normal in all embryos and in the corresponding visceral yolk sacs pretreated at 2.5 hr (but not at 18 hr) after culturing for 24 hr in L-BSO-free medium. GSH content was significantly lower in yolk sacs but not in embryos of conceptuses cultured for 24 hr in medium containing 1 mM L-BSO. This treatment, however, significantly increased the amount of protein and DNA in the embryo. The differential sensitivity of the yolk sac versus embryo and the demonstration of the ability to modulate tissue levels of GSH during organogenesis promise to provide important new tools for the study of embryonic protective mechanisms in chemical teratogenesis.