Effect of Thiol Compounds on in Vitro Development and Intracellular Glutathione Content of Bovine Embryos

The purpose of this investigation was to determine the effect of beta-mercaptoethanol (beta-ME) and cysteamine, low-molecular-weight thiol compounds, on the development and intracellular glutathione content of bovine embryos obtained by in vitro fertilization of in vitro-matured oocytes. Embryos developed to the 6-8-cell stage after in vitro fertilization were cultured without feeder cells in TCM-199 containing 10% fetal calf serum with or without beta-ME or cysteamine. The percentage of embryos that developed to the blastocyst and hatched blastocyst stages were significantly higher in medium containing beta-ME or cysteamine. Also, total intracellular glutathione levels were higher for embryos cultured in the medium with beta-ME or cysteamine than for those cultured in medium without thiol compounds. Moreover, when buthionine sulfoximine, a specific inhibitor of glutathione synthesis, was added to medium containing thiol compounds, there was a reduction both in the development of embryos to the blastocyst stage and in intracellular glutathione content. These results indicate that the inclusion of low-molecular-weight thiol compounds aids the in vitro development of bovine embryos without feeder cells and that the effect of thiol compounds is mediated through the increase of intracellular glutathione levels.