Culture of preimplantation embryos in media containing L-proline increases intracellular GSH concentration throughout development

Careful balance of the redox status of the embryo and reduction of oxidative stress is crucial in early development. Here we show that the culture of preimplantation mouse embryos in the conditionally non-essential amino acid L-proline (Pro) increases the intracellular concentration of the potent antioxidant glutathione as shown by staining of 2-cell, 4-cell and 8-cell embryos with tetrafluoroterephthalonitrile (4F-2CN). Further, liquid-chromatography/mass spectrometry showed increased GSH levels in all Pro-treated preimplantation stages of development compared to controls. The GSH:GSSG ratio also showed a Pro-dependent increase. Overall, our results indicate that the beneficial effect of Pro in preimplantation embryo culture is due to the reduction in oxidative stress mediated through an increase in cellular GSH concentration.