STIMULATION OF GLUTATHIONE SYNTHESIS OF IN-VITRO MATURED BOVINE OOCYTES AND ITS EFFECT ON EMBRYO DEVELOPMENT AND FREEZABILITY

Glutathione (GSH) has been shown to play an important role in embryo d evelopment. In a previous study, we demonstrated that cysteamine suppl ementation of in vitro maturation (IVM) medium increased the intracell ular GSH content in bovine oocytes and improved subsequent embryo deve lopment to the blastocyst stage. The present study was carried out to evaluate the effect of inhibition by buthionine sulfoximide (BSO) of G SH synthesis during IVM in the presence of cysteamine, on subsequent e mbryo development, and the effect of cysteamine during IVM on the surv ival of blastocysts following freezing. The effect of P-mercaptoethano l and cysteine added to the maturation medium on GSH levels in bovine oocytes, as well as the effect of these compounds on de novo GSH synth esis by oocytes during in vitro maturation, was also studied. The inhi bitory effect of BSO during in vitro maturation on GSH synthesis was a lso evaluated. Evidence was found confirming that GSH Synthesis occurs intracellularly during IVM of oocytes and is stimulated by cysteamine , p-mercaptoethanol and cysteine. Moreover, the present results sugges t that the increase in the rate of embryo development exerted by cyste amine, when present during IVM, was due to its stimulatory effect on G SH synthesis. This increase in GSH levels during IVM improves embryo d evelopment and quality, producing more embryos reaching the blastocyst stage on day 6, those most suitable for freezing. (C) 1996 Wiley-Liss , Inc.